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Large reversible magnetostrictive effect in the Gd1−xSmxMn2Ge2 (x = 0.37, 0.34) alloys at room temperature
Journal of Alloys and Compounds 628 (2015) 146–150
Contents lists available at ScienceDirect
Journal of Alloys and Compounds journal homepage: www.elsevier.com/locate/jalcom
Large reversible magnetostrictive effect in the Gd1xSmxMn2Ge2 (x = 0.37, 0.34) alloys at room temperature Y.Y. Gong a,b, L. Zhang c, Q.Q. Cao a,b, D.H. Wang a,b,⇑, Y.W. Du a,b a
National Laboratory of Solid State Microstructures and Jiangsu Key Laboratory for Nano Technology, Nanjing University, Nanjing 210093, People’s Republic of China Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, People’s Republic of China c High Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei 230031, People’s Republic of China b
a r t i c l e
i n f o
Article history: Received 15 October 2014 Received in revised form 20 December 2014 Accepted 23 December 2014 Available online 30 December 2014 Keywords: Reversible magnetostrictive effect Magnetoelastic transition Magnetic-field-induced transition High stability
a b s t r a c t The metamagnetic transition and magnetic-field-induced strain are investigated in the Gd66Sm34 and Gd63Sm37 alloys. The thermal- or magnetic-field-induced magnetoelastic transitions are observed in these alloys at room temperature, which are accompanied by large lattice distortion and minimal hysteresis. Large reversible magnetostriction of 900 and 350 ppm can be obtained in the Gd63Sm37 alloy at 290 K with the magnetic fields of 1 T and 0.5 T, respectively. This excellent magnetostrictive performance is attributed to the lattice change during the magnetic-field-induced magnetoelastic transition. Ó 2014 Elsevier B.V. All rights reserved.
1. Introduction Magnetic-field-induced strain (MFIS) at room temperature has drawn much attention due to its potential applications in actuators, sensors, energy-harvesting and magnetomechanical devices [1,2]. It is reported that the ternary ferromagnetic shape memory alloys Ni–Mn–Z (Z = Ga, In, Sn, Sb) with Heusler type usually show a giant MFIS [3–9]. In Ni–Mn–Ga single crystals with a modulated seven-layered martensite structure (7 M), the corresponding MFIS reaches up to 10% [10], which is generated from the magneticfield-induced twin boundary motion. However, complicated preparation of single crystal hinders its application [11]. Different from Ni–Mn–Ga, the magnetostrain in Ni–Mn–In (Sn, Sb) stems from the magnetic-field-induced first-order magnetostructural transition, i.e. converse martensitic transformation, from low temperature martensite to high temperature austenite. Though these alloys show large MFIS, they still have some drawbacks due to the nature of magnetostructural transition, such as pronounced hysteretic phenomena, irreversibility of the effect, or poor stability [9,10,12,13]. Besides magnetostructural transition, large lattice distortion also appears in magnetoelastic transition and the MFIS generated from this transition is highly reversible [14–16]. For ⇑ Corresponding author at: National Laboratory of Solid State Microstructures, Jiangsu Key Laboratory for Nano Technology and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, People’s Republic of China. E-mail address: [email protected] (D.H. Wang). http://dx.doi.org/10.1016/j.jallcom.2014.12.132 0925-8388/Ó 2014 Elsevier B.V. All rights reserved.
example, in La(Fe1xSix)13Hy and Gd5(SixGe1x)4 alloys, large strain can be induced almost reversibly by applying an external magnetic field [14–16]. Thus, for obtaining reversible MFIS, magnetoelastic transition is more suitable than magnetostructural transition. However, magnetoelastic transitions usually need high driving magnetic field and occur far from room temperature [14–19], so it is still a great challenge for exploring a material showing large low-field MFIS at room temperature. Recently, the intermetallic compounds of RMn2X2 (R = rare earth elements; X = Si or Ge) with the ThCr2Si2-type structure have attracted ever-increasing interest due to their abundant physical phenomena, such as giant magnetoresistance, magnetocaloric effect, complicated magnetic phase transitions [20]. The atomic framework of this structure can be understood as equivalent separate atomic layers staked along the tetragonal c axis in a sequence of R–X–Mn–X–R–X–Mn–X–R [20]. With increasing temperature, a series of transitions from interlayer antiferromagnetism (AFM I) ? interlayer ferromagnetism (FM) ? collinear antiferromagnetism (AFM II) ? paramagnetism (PM) are observed in these alloys due to the variation of exchange interaction [21–27]. It is known that the transition between AFM I and FM is strongly depended on the Mn–Mn distance [20–27], and there exists a critical in-plane MnMn Mn–Mn distance (dc ) in this system, above which magnetic moments of Mn in the adjacent layers are ordered ferromagnetically while below which the AFM I ordering is realized [21–27]. When Mn–Mn distance is close to the critical value, a first-order phase transition between AFM I and FM phases can be easily induced by temperature or magnetic field [22–27]. Moreover, this magnetic
Y.Y. Gong et al. / Journal of Alloys and Compounds 628 (2015) 146–150
transition is reported to be very sensitive to the pressure as well [28,29]. For example, the transition temperature in the La0.75Sm0.25 Mn2Si2 alloy increases rapidly by increasing the pressure at a rate of 203 K/GPa [29]. According to the Clausius–Clapeyron thermodynamic relation:
dT AFM I!FM DV dT AFM I!FM ¼ dP DM dH
ð1Þ
where DM and DV are the difference in magnetization and volume I!FM between AFM I and FM state, respectively; dT AFMdPI!FM and dT AFM are dH the change of AFM I ? FM transition temperature by applying pressure and magnetic field, respectively. The calculated DV indicates that the AFM I ? FM magnetic phase transition is accompanied by a significant volume change [29]. Since this transition can be driven by magnetic field as well [23,25,26,29], a large MFIS is expected in RMn2X2 system. In this paper, the magnetostriction effect of the Gd1xSmxMn2Ge2 alloys is investigated. By tuning the ratio of Gd and Sm, thermal- or magnetic-field-induced AFM I ? FM phase transitions are obtained at room temperature. Furthermore, we demonstrate that the corresponding magnetic transition is a firstorder magnetoelastic one, which couples with large lattice distortion and low driving field. As a result, large reversible low-field magnetostriction (900 ppm) with minimal hysteresis and high stability is observed in this system due to the magnetic-field-induced metamagnetic transition.
2. Experiment The polycrystalline alloys of Gd0.63Sm0.37Mn2Ge2 (Gd63Sm37) and Gd0.66Sm0.34 Mn2Ge2 (Gd66Sm34) were obtained by induction melting the corresponding elements in an argon atmosphere for three times. Then the ingots were sealed in a quartz tube for further annealing at 1023 K for 1 week. Some plates with dimensions of 8 mm 5 mm 1 mm were cut from the samples for magnetostriction measurement. The structure and lattice parameters of the alloys were verified by X-ray diffraction (XRD) in the temperature range of 280–340 K. Magnetic measurements were carried out by a superconducting quantum interference device (SQUID, Quantum Design) and a vibrating sample magnetometer (VSM, LakeShore). Magnetostriction measurement was performed using a standard strain-gauge technique on a physical property measurement system (PPMS, Quantum Design).
147
weak magnetization state to a ferromagnetic state is induced at 260 K, as shown in the inset of Fig. 1. According to the earlier reports about the magnetic transitions in the Gd1xSmxMn2Ge2 alloys [23], this metamagnetic behavior corresponds to the transition from AFM I state to FM state. Unlike the Gd66Sm34 alloy, this type of transition can be obviously observed in the Gd63Sm37 alloy at T1 = 295 K with a magnetic field of 0.01 T, suggesting the decrease of critical field for driving metamagnetic transition. Further heating leads to another sharp transition from FM state to AFM II state at T2 = 340 K. It is evident that the thermal hysteresis between heating and cooling process for these two alloys is less than 1 K, which is consistent with the earlier reports of Gd1xSmx Mn2Ge2 alloys [23]. The irreversibility in the temperature range from 295 to 340 K is due to cooling from the AFM II state to 340 K in an external magnetic field, which would give a preferred orientation to ferromagnetic components [26]. To further investigate the AFM I ? FM transition in the present system, the temperature dependence of XRD patterns for these two alloys is measured. The results of diffraction patterns demonstrate that the samples crystallize in the ThCr2Si2 structure and retain it unchanged after undergoing the phase transition, which is in agreement with the results in the RMn2X2 system [22–27], suggesting that the AFM I ? FM transition in the Gd66Sm34 and Gd63Sm37 alloys is a magnetoelastic one [22–26]. According to the XRD patterns, the variations of lattice constants a and c as functions of temperature are calculated, as shown in Fig. 2. The values of c in both alloys increase gently with increasing temperature. As for the values of a, they increase more quickly as the temperature grows. Moreover, an abrupt increase of a of about 0.16% is observed in the Gd63Sm37 alloy around the transition temperature, suggesting that a large MFIS would be obtained in this alloy. As mentioned above, the magnetic ordering of interlayer Mn atoms has an intimate relation with the interlayer Mn–Mn
3. Results and discussion The temperature dependence of magnetization (M–T) for the Gd66Sm34 and Gd63Sm37 alloys with an applied field of 0.01 T is shown in Fig. 1. It can be seen that the Gd66Sm34 sample shows a weak magnetic state and no obvious thermal-induced metamagnetic transition is observed at this low magnetic field. However, in a high magnetic field of 3 T, a metamagnetic transition from a
Fig. 1. The temperature dependence of magnetization for the Gd66Sm34 and Gd63Sm37 alloys in an applied field of 0.01 T. Inset: The temperature dependence of magnetization for the Gd66Sm34 alloy in an applied field of 3 T.
Fig. 2. The temperature dependence of lattice constants a and c for the (a) Gd66Sm34 and (b) Gd63Sm37 alloys.
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pffiffiffi MnMn distance and dc defined as a/ 2 ranges from 0.2850 to 0.2870 nm in the RMn2X2 system [21–23,29]. Table 1 shows the values of Mn–Mn distance for the two alloys around the AFM I ? FM transition. By considering both the M–T curves in Fig. 1 MnMn and Table 1, dc of the Gd1xSmxMn2Ge2 system is determined to be about 0.2861 nm. For the Gd66Sm34 alloy, the values of Mn– Mn distance change from 0.2855 to 0.2859 nm with the temperaMnMn ture varying from 300 to 330 K, which are all less than dc , leading to the AFM I ordering in this temperature range (as shown in Fig. 1). However, in the case of the Gd63Sm37 alloy, the values of Mn–Mn distance are 0.2861 nm and 0.2865 nm for 290 K and 310 K, respectively, which results in different magnetic ordering at these two different temperatures. Since Mn–Mn distance at MnMn 290 K is extremely close to dc , the competition between AFM I and FM state is relatively easy to be broken. Thus, a thermal-induced AFM I ? FM transition can be observed in the Gd63 Sm37 alloy around 295 K. Moreover, a high magnetic field would have the same effect to overcome the competition and induce the AFM I ? FM transition as well. This is the origin of the metamagnetic transition in the Gd66Sm34 alloy at 3 T, as shown in the inset of Fig. 1. Fig. 3(a) shows the isothermal magnetization (M–H) curves for the Gd66Sm34 alloy measured in the temperature range from 280 to 310 K with increasing and decreasing magnetic fields, in which a series of metamagnetic transitions from weak magnetic AFM I state to FM state are observed. The critical field for driving metamagnetic transition, which is defined as the inflection point in the M–H curve [30], decreases with increasing temperature. As shown in Fig. 3(b), similar M–H curves are observed in the Gd63 Sm37 alloy except the critical field is reduced. It is known that SmMn2Ge2 is FM while GdMn2Ge2 is AFM in the temperature range from 200 to 350 K [21,28]. Therefore, the substitution of Sm for Gd would introduce a FM component in the alloy, which makes FM state more dominate in the AFM I-FM competition. As a result, increasing the content of Sm would decrease critical field in the Gd63Sm37 alloy. Moreover, it is obvious that the magnetic hysteresis for these two alloys is very low (almost 300 Oe), which is of great importance for the practical applications. The magnetic field dependence of strain (k = DL/L) for the Gd66 Sm34 and Gd63Sm37 alloys measured around room temperature are shown in Fig. 4(a) and (b), respectively. Here the measuring direction is parallel to the magnetic field. Due to the polycrystalline nature of our samples, this volume magnetostriction is isotropic, which is consistent with other magnetoelastic transition alloys [18,31]. Despite the direction of magnetic field, the values of transverse and longitudinal magnetostriction generated from the magnetic-field-induced metamagnetic transition are equal in the Gd66Sm34 and Gd63Sm37 alloys (not shown here). As shown in Fig. 4(a) and (b), it is obvious that large reversible MFIS with minimal hysteresis are obtained in these two alloys with
Table 1 The values of Mn–Mn distance for the Gd66Sm34 and Gd63Sm37 alloys at different temperature. Gd66Sm34
Gd63Sm37
Temperature (K)
Mn–Mn distance (nm)
Temperature (K)
Mn–Mn distance (nm)
200 240 270 300 310 320 330 350 360
0.2852(8) 0.2853(4) 0.2853(8) 0.2855(1) 0.2856(0) 0.2857(3) 0.2858(6) 0.2859(4) 0.2859(9)
200 240 270 290 300 310 320 350 360
0.2860(1) 0.2860(6) 0.2860(7) 0.2861(0) 0.2862(0) 0.2865(4) 0.2865(6) 0.2865(8) 0.2865(9)
Fig. 3. Isothermal magnetization curves for the (a) Gd66Sm34 and (b) Gd63Sm37 alloys.
increasing and decreasing magnetic fields. The similarity between Figs. 3 and 4 gives a suggestion that the strain would be generated from the magnetic-field-induced magnetoelastic transition. As for the Gd66Sm34 alloy, its MFIS reaches up to 900 ppm under a magnetic field of 2 T at 300 K. With the decrease of temperature, higher magnetic field is needed to obtain the MFIS with the same order. It is worth noting that a same MFIS of 900 ppm can be obtained in the Gd63Sm37 alloy at 290 K, but the driving field is significantly reduced to 1 T, as shown in Fig. 4(b). Obviously, the large reversible and low-field MFIS at room temperature in the Gd63Sm37 alloy is of great importance for the practical application. In untextured polycrystalline material, the strain generated from the AFM I ? FM transition is isotropic and can be described as [31]:
DL=L ¼ 2Da=3a:
ð2Þ
Here, Da/a is the change of lattice constant a during the AFM I ? FM transition. According to the result mentioned above (Da/a 0.16%), the calculated DL/L is 0.106%, which agrees with the experimental results. In the present system, large MFIS is attributed to the lattice distortion during the magnetoelastic transition from the AFM I state to the FM state, which is a different magnetostrictive mechanism from that of RFe2 alloys [32]. Similarly, the MFIS in the ternary ferromagnetic shape memory alloys Ni–Mn–Z is also generated from the magnetic-field-induced phase transition. However, this magnetostructural transition couples with large hysteresis, high driving field and poor stability, which restricts their utility for applications [9–13]. Compared with the magnetostructural transition, the MFIS in the Gd63Sm37 alloy can overcome the aforementioned weaknesses. Large reversible MFIS of 900 and 350 ppm can be obtained at room temperature under a magnetic field of 1 T and
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the unchanged values of magnetostrain are obtained in each cycle. The average saturate value of MFIS is 964.9 ppm at 2 T and the corresponding standard deviation is 3.7 ppm. Accordingly, the deviation values in the first and last cycle are 6.9 and 4.7 ppm, respectively, which indicates the good reversibility and high stability of MFIS behavior in our sample. 4. Conclusion In summary, by tuning the ratio of Gd and Sm, the Mn–Mn distance in Gd1xSmxMn2Ge2 system is adjusted to be close to the MnMn dc , which leads to the thermal- and magnetic-field-induced magnetoelastic transition in the Gd66Sm34 and Gd63Sm37 alloys around room temperature. Large reversible MFIS with minimal hysteresis and high stability is obtained in the Gd63Sm37 alloy under low magnetic field. The magnetostriction performance in this alloy suggests the promising applications in actuators, sensors and magnetomechanical devices. Acknowledgements This work is supported by the National Natural Science Foundation of China (Grant Nos. 51371184 and U1232210). References
Fig. 4. The magnetic field dependence of strain measured around room temperature for the (a) Gd66Sm34 and (b) Gd63Sm37 alloys.
Fig. 5. Magnetostrain of Gd63Sm37 alloy versus time signals at 290 K with application and removal of the magnetic field.
0.5 T, respectively, which is comparable to some famous RFe2-based magnetostrictive material [33–35]. In order to investigate the stability of the magnetostrictive response, we measure the MFIS of Gd63Sm37 alloy by repeatedly switching on/off the 2 T magnetic field for 10 cycles at 290 K, as shown in Fig. 5. Application and removal of the magnetic field creates a tower shape response of MFIS versus time evolution, while
[1] S.A. Wilson, R.P.J. Jourdain, Q. Zhang, R.A. Dorey, C.R. Bowen, M. Willander, Q.U. Wahab, M. Willander, S.M. Al-hilli, O. Nur, E. Quandt, C. Johansson, E. Pagounis, M. Kohl, J. Matovic, B. Samel, W. van der Wijngaart, E.W.H. Jager, D. Carlsson, Z. Djinovic, M. Wegener, C. Moldovan, R. Iosub, E. Abad, M. Wendlandt, C. Rusug, K. Persson, Mater. Sci. Eng., R 56 (2007) 1. [2] A.G. Olabi, A. Grunwald, Mater. Des. 29 (2008) 469. [3] O. Söderberg, A. Sozinov, Y. Ge, S.-P. Hannula, V.K. Lindroos, in: K.H.J. Buschow (Ed.), Handbook of Magnetic Materials, vol. 16, Elsevier, Amsterdam, 2006, p. 1. [4] S.J. Murray, M. Marioni, S.M. Allen, R.C. O’Handley, Appl. Phys. Lett. 77 (2000) 886. [5] M. Chmielus, X.X. Zhang, C. Witherspoon, D.C. Dunand, P. Müllner, Nat. Mater. 8 (2009) 863. [6] R. Kainuma, Y. Imano, W. Ito, Y. Sutou, H. Morito, S. Okamoto, O. Kitakami, K. Oikawa, A. Fujita, T. Kanomata, K. Ishida, Nature 439 (2006) 957. [7] R. Kainuma, Y. Imano, W. Ito, Y. Sutou, K. Oikawa, A. Fujita, K. Ishida, S. Okamoto, O. Kitakami, T. Kanomata, Appl. Phys. Lett. 88 (2006) 192513. [8] J. Liu, S. Aksoy, N. Scheerbaum, M. Acet, O. Gutfleisch, Appl. Phys. Lett. 95 (2009) 232515. [9] Z. Li, C. Jing, H.L. Zhang, D.H. Yu, L. Chen, B.J. Kang, S.X. Cao, J.C. Zhang, J. Appl. Phys. 108 (2010) 113908. [10] A. Sozinov, A.A. Likhachev, N. Lanska, O. Söderberg, K. Ullakko, V.K. Lindroos, Mater. Sci. Eng., A 378 (2004) 399. [11] J. Liu, N. Scheerbaum, S. Kauffmann-Weiss, O. Gutfleisch, Adv. Eng. Mater. 14 (2012) 653. [12] V.V. Khovaylo, K.P. Skokov, O. Gutfleisch, H. Miki, R. Kainuma, T. Kanomata, Appl. Phys. Lett. 97 (2010) 052503. [13] J. Liu, N. Scheerbaum, J. Lyubina, O. Gutfleisch, Appl. Phys. Lett. 93 (2008) 102512. [14] F.X. Hu, B.G. Shen, J.R. Sun, Z.H. Cheng, G.H. Rao, X.X. Zhang, Appl. Phys. Lett. 78 (2001) 3675. [15] S. Fujieda, A. Fujita, K. Fukamichi, Y. Yamazaki, Y. Iijima, Appl. Phys. Lett. 79 (2001) 653. [16] L. Morellon, P.A. Algarabel, M.R. Ibarra, J. Blasco, B. García-Landa, Z. Arnold, F. Albertini, Phys. Rev. B 58 (1998) R14721. [17] Z. Gercsi, E.K. Delczeg-Czirjak, L. Vitos, A.S. Wills, A. Daoud-Aladine, K.G. Sandeman, Phys. Rev. B 88 (2013) 024417. [18] M.I. Bartashevich, T. Goto, N.V. Baranov, V.S. Gaviko, Physica B 351 (2004) 71. [19] S.C. Ma, D. Hou, Y.Y. Gong, L.Y. Wang, Y.L. Huang, Z.C. Zhong, D.H. Wang, Y.W. Du, Appl. Phys. Lett. 104 (2014) 022410. [20] A. Szytuła, in: K.H.J. Buschow (Ed.), Handbook of Magnetic Materials, vol. 6, Elsevier, Amsterdam, 1991, p. 85. [21] M. Duraj, A. Szytuła, Acta Phys. Pol., A 117 (2010) 603. [22] H. Fujii, T. Okamoto, T. Shigeoka, N. Iwata, Solid State Commun. 53 (1985) 715. [23] P. Kumar, N.K. Singh, K.G. Suresh, A.K. Nigam, S.K. Malik, J. Phys.: Condens. Matter 19 (2007) 386210. [24] E.G. Gerasimov, R.Y. Umetsu, N.V. Mushnikov, A. Fujita, T. Kanomata, J. Phys.: Condens. Matter 19 (2007) 486202. [25] E.G. Gerasimov, V.S. Gaviko, V.N. Neverov, A.V. Korolyov, J. Alloys Comp. 343 (2002) 14. [26] B. Emre, I. Dincer, Y. Elerman, E. Duman, Phys. Scr. 80 (2009) 055703. [27] G. Venturini, R. Welter, E. Ressouche, B. Malaman, J. Alloys Comp. 223 (1995) 101.
150
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[28] P. Kumar, K.G. Suresh, A.K. Nigam, A. Magnus, A.A. Coelho, S. Gama, Phys. Rev. B 77 (2008) 224427. [29] E.G. Gerasimov, N.V. Mushnikov, Phys. Rev. B 72 (2005) 064446. [30] C.L. Zhang, Y.X. Zheng, H.C. Xuan, S.C. Ma, Q.Q. Cao, D.H. Wang, Y.W. Du, J. Phys. D Appl. Phys. 44 (2011) 135003. [31] G.H. Guo, Y. Wu, H.B. Zhang, D.A. Filippov, R.Z. Levitin, V.V. Snegirev, Chin. Phys. 11 (2002) 608.
[32] A.E. Clark, in: K.H.J. Buschow (Ed.), Handbook of Magnetic Materials, vol. 1, Elsevier, Amsterdam, 1980, p. 531. [33] B.W. Wang, S.L. Tang, X.M. Jin, L.Z. Cheng, K.Y. He, Appl. Phys. Lett. 69 (1996) 3429. [34] L. Xu, C.B. Jiang, H.B. Xu, Appl. Phys. Lett. 89 (2006) 192507. [35] K. Prajapati, A.G. Jenner, M.P. Schulze, R.D. Greenough, J. Appl. Phys. 73 (1993) 6171.
Contents lists available at ScienceDirect
Journal of Alloys and Compounds journal homepage: www.elsevier.com/locate/jalcom
Large reversible magnetostrictive effect in the Gd1xSmxMn2Ge2 (x = 0.37, 0.34) alloys at room temperature Y.Y. Gong a,b, L. Zhang c, Q.Q. Cao a,b, D.H. Wang a,b,⇑, Y.W. Du a,b a
National Laboratory of Solid State Microstructures and Jiangsu Key Laboratory for Nano Technology, Nanjing University, Nanjing 210093, People’s Republic of China Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, People’s Republic of China c High Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei 230031, People’s Republic of China b
a r t i c l e
i n f o
Article history: Received 15 October 2014 Received in revised form 20 December 2014 Accepted 23 December 2014 Available online 30 December 2014 Keywords: Reversible magnetostrictive effect Magnetoelastic transition Magnetic-field-induced transition High stability
a b s t r a c t The metamagnetic transition and magnetic-field-induced strain are investigated in the Gd66Sm34 and Gd63Sm37 alloys. The thermal- or magnetic-field-induced magnetoelastic transitions are observed in these alloys at room temperature, which are accompanied by large lattice distortion and minimal hysteresis. Large reversible magnetostriction of 900 and 350 ppm can be obtained in the Gd63Sm37 alloy at 290 K with the magnetic fields of 1 T and 0.5 T, respectively. This excellent magnetostrictive performance is attributed to the lattice change during the magnetic-field-induced magnetoelastic transition. Ó 2014 Elsevier B.V. All rights reserved.
1. Introduction Magnetic-field-induced strain (MFIS) at room temperature has drawn much attention due to its potential applications in actuators, sensors, energy-harvesting and magnetomechanical devices [1,2]. It is reported that the ternary ferromagnetic shape memory alloys Ni–Mn–Z (Z = Ga, In, Sn, Sb) with Heusler type usually show a giant MFIS [3–9]. In Ni–Mn–Ga single crystals with a modulated seven-layered martensite structure (7 M), the corresponding MFIS reaches up to 10% [10], which is generated from the magneticfield-induced twin boundary motion. However, complicated preparation of single crystal hinders its application [11]. Different from Ni–Mn–Ga, the magnetostrain in Ni–Mn–In (Sn, Sb) stems from the magnetic-field-induced first-order magnetostructural transition, i.e. converse martensitic transformation, from low temperature martensite to high temperature austenite. Though these alloys show large MFIS, they still have some drawbacks due to the nature of magnetostructural transition, such as pronounced hysteretic phenomena, irreversibility of the effect, or poor stability [9,10,12,13]. Besides magnetostructural transition, large lattice distortion also appears in magnetoelastic transition and the MFIS generated from this transition is highly reversible [14–16]. For ⇑ Corresponding author at: National Laboratory of Solid State Microstructures, Jiangsu Key Laboratory for Nano Technology and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, People’s Republic of China. E-mail address: [email protected] (D.H. Wang). http://dx.doi.org/10.1016/j.jallcom.2014.12.132 0925-8388/Ó 2014 Elsevier B.V. All rights reserved.
example, in La(Fe1xSix)13Hy and Gd5(SixGe1x)4 alloys, large strain can be induced almost reversibly by applying an external magnetic field [14–16]. Thus, for obtaining reversible MFIS, magnetoelastic transition is more suitable than magnetostructural transition. However, magnetoelastic transitions usually need high driving magnetic field and occur far from room temperature [14–19], so it is still a great challenge for exploring a material showing large low-field MFIS at room temperature. Recently, the intermetallic compounds of RMn2X2 (R = rare earth elements; X = Si or Ge) with the ThCr2Si2-type structure have attracted ever-increasing interest due to their abundant physical phenomena, such as giant magnetoresistance, magnetocaloric effect, complicated magnetic phase transitions [20]. The atomic framework of this structure can be understood as equivalent separate atomic layers staked along the tetragonal c axis in a sequence of R–X–Mn–X–R–X–Mn–X–R [20]. With increasing temperature, a series of transitions from interlayer antiferromagnetism (AFM I) ? interlayer ferromagnetism (FM) ? collinear antiferromagnetism (AFM II) ? paramagnetism (PM) are observed in these alloys due to the variation of exchange interaction [21–27]. It is known that the transition between AFM I and FM is strongly depended on the Mn–Mn distance [20–27], and there exists a critical in-plane MnMn Mn–Mn distance (dc ) in this system, above which magnetic moments of Mn in the adjacent layers are ordered ferromagnetically while below which the AFM I ordering is realized [21–27]. When Mn–Mn distance is close to the critical value, a first-order phase transition between AFM I and FM phases can be easily induced by temperature or magnetic field [22–27]. Moreover, this magnetic
Y.Y. Gong et al. / Journal of Alloys and Compounds 628 (2015) 146–150
transition is reported to be very sensitive to the pressure as well [28,29]. For example, the transition temperature in the La0.75Sm0.25 Mn2Si2 alloy increases rapidly by increasing the pressure at a rate of 203 K/GPa [29]. According to the Clausius–Clapeyron thermodynamic relation:
dT AFM I!FM DV dT AFM I!FM ¼ dP DM dH
ð1Þ
where DM and DV are the difference in magnetization and volume I!FM between AFM I and FM state, respectively; dT AFMdPI!FM and dT AFM are dH the change of AFM I ? FM transition temperature by applying pressure and magnetic field, respectively. The calculated DV indicates that the AFM I ? FM magnetic phase transition is accompanied by a significant volume change [29]. Since this transition can be driven by magnetic field as well [23,25,26,29], a large MFIS is expected in RMn2X2 system. In this paper, the magnetostriction effect of the Gd1xSmxMn2Ge2 alloys is investigated. By tuning the ratio of Gd and Sm, thermal- or magnetic-field-induced AFM I ? FM phase transitions are obtained at room temperature. Furthermore, we demonstrate that the corresponding magnetic transition is a firstorder magnetoelastic one, which couples with large lattice distortion and low driving field. As a result, large reversible low-field magnetostriction (900 ppm) with minimal hysteresis and high stability is observed in this system due to the magnetic-field-induced metamagnetic transition.
2. Experiment The polycrystalline alloys of Gd0.63Sm0.37Mn2Ge2 (Gd63Sm37) and Gd0.66Sm0.34 Mn2Ge2 (Gd66Sm34) were obtained by induction melting the corresponding elements in an argon atmosphere for three times. Then the ingots were sealed in a quartz tube for further annealing at 1023 K for 1 week. Some plates with dimensions of 8 mm 5 mm 1 mm were cut from the samples for magnetostriction measurement. The structure and lattice parameters of the alloys were verified by X-ray diffraction (XRD) in the temperature range of 280–340 K. Magnetic measurements were carried out by a superconducting quantum interference device (SQUID, Quantum Design) and a vibrating sample magnetometer (VSM, LakeShore). Magnetostriction measurement was performed using a standard strain-gauge technique on a physical property measurement system (PPMS, Quantum Design).
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weak magnetization state to a ferromagnetic state is induced at 260 K, as shown in the inset of Fig. 1. According to the earlier reports about the magnetic transitions in the Gd1xSmxMn2Ge2 alloys [23], this metamagnetic behavior corresponds to the transition from AFM I state to FM state. Unlike the Gd66Sm34 alloy, this type of transition can be obviously observed in the Gd63Sm37 alloy at T1 = 295 K with a magnetic field of 0.01 T, suggesting the decrease of critical field for driving metamagnetic transition. Further heating leads to another sharp transition from FM state to AFM II state at T2 = 340 K. It is evident that the thermal hysteresis between heating and cooling process for these two alloys is less than 1 K, which is consistent with the earlier reports of Gd1xSmx Mn2Ge2 alloys [23]. The irreversibility in the temperature range from 295 to 340 K is due to cooling from the AFM II state to 340 K in an external magnetic field, which would give a preferred orientation to ferromagnetic components [26]. To further investigate the AFM I ? FM transition in the present system, the temperature dependence of XRD patterns for these two alloys is measured. The results of diffraction patterns demonstrate that the samples crystallize in the ThCr2Si2 structure and retain it unchanged after undergoing the phase transition, which is in agreement with the results in the RMn2X2 system [22–27], suggesting that the AFM I ? FM transition in the Gd66Sm34 and Gd63Sm37 alloys is a magnetoelastic one [22–26]. According to the XRD patterns, the variations of lattice constants a and c as functions of temperature are calculated, as shown in Fig. 2. The values of c in both alloys increase gently with increasing temperature. As for the values of a, they increase more quickly as the temperature grows. Moreover, an abrupt increase of a of about 0.16% is observed in the Gd63Sm37 alloy around the transition temperature, suggesting that a large MFIS would be obtained in this alloy. As mentioned above, the magnetic ordering of interlayer Mn atoms has an intimate relation with the interlayer Mn–Mn
3. Results and discussion The temperature dependence of magnetization (M–T) for the Gd66Sm34 and Gd63Sm37 alloys with an applied field of 0.01 T is shown in Fig. 1. It can be seen that the Gd66Sm34 sample shows a weak magnetic state and no obvious thermal-induced metamagnetic transition is observed at this low magnetic field. However, in a high magnetic field of 3 T, a metamagnetic transition from a
Fig. 1. The temperature dependence of magnetization for the Gd66Sm34 and Gd63Sm37 alloys in an applied field of 0.01 T. Inset: The temperature dependence of magnetization for the Gd66Sm34 alloy in an applied field of 3 T.
Fig. 2. The temperature dependence of lattice constants a and c for the (a) Gd66Sm34 and (b) Gd63Sm37 alloys.
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pffiffiffi MnMn distance and dc defined as a/ 2 ranges from 0.2850 to 0.2870 nm in the RMn2X2 system [21–23,29]. Table 1 shows the values of Mn–Mn distance for the two alloys around the AFM I ? FM transition. By considering both the M–T curves in Fig. 1 MnMn and Table 1, dc of the Gd1xSmxMn2Ge2 system is determined to be about 0.2861 nm. For the Gd66Sm34 alloy, the values of Mn– Mn distance change from 0.2855 to 0.2859 nm with the temperaMnMn ture varying from 300 to 330 K, which are all less than dc , leading to the AFM I ordering in this temperature range (as shown in Fig. 1). However, in the case of the Gd63Sm37 alloy, the values of Mn–Mn distance are 0.2861 nm and 0.2865 nm for 290 K and 310 K, respectively, which results in different magnetic ordering at these two different temperatures. Since Mn–Mn distance at MnMn 290 K is extremely close to dc , the competition between AFM I and FM state is relatively easy to be broken. Thus, a thermal-induced AFM I ? FM transition can be observed in the Gd63 Sm37 alloy around 295 K. Moreover, a high magnetic field would have the same effect to overcome the competition and induce the AFM I ? FM transition as well. This is the origin of the metamagnetic transition in the Gd66Sm34 alloy at 3 T, as shown in the inset of Fig. 1. Fig. 3(a) shows the isothermal magnetization (M–H) curves for the Gd66Sm34 alloy measured in the temperature range from 280 to 310 K with increasing and decreasing magnetic fields, in which a series of metamagnetic transitions from weak magnetic AFM I state to FM state are observed. The critical field for driving metamagnetic transition, which is defined as the inflection point in the M–H curve [30], decreases with increasing temperature. As shown in Fig. 3(b), similar M–H curves are observed in the Gd63 Sm37 alloy except the critical field is reduced. It is known that SmMn2Ge2 is FM while GdMn2Ge2 is AFM in the temperature range from 200 to 350 K [21,28]. Therefore, the substitution of Sm for Gd would introduce a FM component in the alloy, which makes FM state more dominate in the AFM I-FM competition. As a result, increasing the content of Sm would decrease critical field in the Gd63Sm37 alloy. Moreover, it is obvious that the magnetic hysteresis for these two alloys is very low (almost 300 Oe), which is of great importance for the practical applications. The magnetic field dependence of strain (k = DL/L) for the Gd66 Sm34 and Gd63Sm37 alloys measured around room temperature are shown in Fig. 4(a) and (b), respectively. Here the measuring direction is parallel to the magnetic field. Due to the polycrystalline nature of our samples, this volume magnetostriction is isotropic, which is consistent with other magnetoelastic transition alloys [18,31]. Despite the direction of magnetic field, the values of transverse and longitudinal magnetostriction generated from the magnetic-field-induced metamagnetic transition are equal in the Gd66Sm34 and Gd63Sm37 alloys (not shown here). As shown in Fig. 4(a) and (b), it is obvious that large reversible MFIS with minimal hysteresis are obtained in these two alloys with
Table 1 The values of Mn–Mn distance for the Gd66Sm34 and Gd63Sm37 alloys at different temperature. Gd66Sm34
Gd63Sm37
Temperature (K)
Mn–Mn distance (nm)
Temperature (K)
Mn–Mn distance (nm)
200 240 270 300 310 320 330 350 360
0.2852(8) 0.2853(4) 0.2853(8) 0.2855(1) 0.2856(0) 0.2857(3) 0.2858(6) 0.2859(4) 0.2859(9)
200 240 270 290 300 310 320 350 360
0.2860(1) 0.2860(6) 0.2860(7) 0.2861(0) 0.2862(0) 0.2865(4) 0.2865(6) 0.2865(8) 0.2865(9)
Fig. 3. Isothermal magnetization curves for the (a) Gd66Sm34 and (b) Gd63Sm37 alloys.
increasing and decreasing magnetic fields. The similarity between Figs. 3 and 4 gives a suggestion that the strain would be generated from the magnetic-field-induced magnetoelastic transition. As for the Gd66Sm34 alloy, its MFIS reaches up to 900 ppm under a magnetic field of 2 T at 300 K. With the decrease of temperature, higher magnetic field is needed to obtain the MFIS with the same order. It is worth noting that a same MFIS of 900 ppm can be obtained in the Gd63Sm37 alloy at 290 K, but the driving field is significantly reduced to 1 T, as shown in Fig. 4(b). Obviously, the large reversible and low-field MFIS at room temperature in the Gd63Sm37 alloy is of great importance for the practical application. In untextured polycrystalline material, the strain generated from the AFM I ? FM transition is isotropic and can be described as [31]:
DL=L ¼ 2Da=3a:
ð2Þ
Here, Da/a is the change of lattice constant a during the AFM I ? FM transition. According to the result mentioned above (Da/a 0.16%), the calculated DL/L is 0.106%, which agrees with the experimental results. In the present system, large MFIS is attributed to the lattice distortion during the magnetoelastic transition from the AFM I state to the FM state, which is a different magnetostrictive mechanism from that of RFe2 alloys [32]. Similarly, the MFIS in the ternary ferromagnetic shape memory alloys Ni–Mn–Z is also generated from the magnetic-field-induced phase transition. However, this magnetostructural transition couples with large hysteresis, high driving field and poor stability, which restricts their utility for applications [9–13]. Compared with the magnetostructural transition, the MFIS in the Gd63Sm37 alloy can overcome the aforementioned weaknesses. Large reversible MFIS of 900 and 350 ppm can be obtained at room temperature under a magnetic field of 1 T and
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the unchanged values of magnetostrain are obtained in each cycle. The average saturate value of MFIS is 964.9 ppm at 2 T and the corresponding standard deviation is 3.7 ppm. Accordingly, the deviation values in the first and last cycle are 6.9 and 4.7 ppm, respectively, which indicates the good reversibility and high stability of MFIS behavior in our sample. 4. Conclusion In summary, by tuning the ratio of Gd and Sm, the Mn–Mn distance in Gd1xSmxMn2Ge2 system is adjusted to be close to the MnMn dc , which leads to the thermal- and magnetic-field-induced magnetoelastic transition in the Gd66Sm34 and Gd63Sm37 alloys around room temperature. Large reversible MFIS with minimal hysteresis and high stability is obtained in the Gd63Sm37 alloy under low magnetic field. The magnetostriction performance in this alloy suggests the promising applications in actuators, sensors and magnetomechanical devices. Acknowledgements This work is supported by the National Natural Science Foundation of China (Grant Nos. 51371184 and U1232210). References
Fig. 4. The magnetic field dependence of strain measured around room temperature for the (a) Gd66Sm34 and (b) Gd63Sm37 alloys.
Fig. 5. Magnetostrain of Gd63Sm37 alloy versus time signals at 290 K with application and removal of the magnetic field.
0.5 T, respectively, which is comparable to some famous RFe2-based magnetostrictive material [33–35]. In order to investigate the stability of the magnetostrictive response, we measure the MFIS of Gd63Sm37 alloy by repeatedly switching on/off the 2 T magnetic field for 10 cycles at 290 K, as shown in Fig. 5. Application and removal of the magnetic field creates a tower shape response of MFIS versus time evolution, while
[1] S.A. Wilson, R.P.J. Jourdain, Q. Zhang, R.A. Dorey, C.R. Bowen, M. Willander, Q.U. Wahab, M. Willander, S.M. Al-hilli, O. Nur, E. Quandt, C. Johansson, E. Pagounis, M. Kohl, J. Matovic, B. Samel, W. van der Wijngaart, E.W.H. Jager, D. Carlsson, Z. Djinovic, M. Wegener, C. Moldovan, R. Iosub, E. Abad, M. Wendlandt, C. Rusug, K. Persson, Mater. Sci. Eng., R 56 (2007) 1. [2] A.G. Olabi, A. Grunwald, Mater. Des. 29 (2008) 469. [3] O. Söderberg, A. Sozinov, Y. Ge, S.-P. Hannula, V.K. Lindroos, in: K.H.J. Buschow (Ed.), Handbook of Magnetic Materials, vol. 16, Elsevier, Amsterdam, 2006, p. 1. [4] S.J. Murray, M. Marioni, S.M. Allen, R.C. O’Handley, Appl. Phys. Lett. 77 (2000) 886. [5] M. Chmielus, X.X. Zhang, C. Witherspoon, D.C. Dunand, P. Müllner, Nat. Mater. 8 (2009) 863. [6] R. Kainuma, Y. Imano, W. Ito, Y. Sutou, H. Morito, S. Okamoto, O. Kitakami, K. Oikawa, A. Fujita, T. Kanomata, K. Ishida, Nature 439 (2006) 957. [7] R. Kainuma, Y. Imano, W. Ito, Y. Sutou, K. Oikawa, A. Fujita, K. Ishida, S. Okamoto, O. Kitakami, T. Kanomata, Appl. Phys. Lett. 88 (2006) 192513. [8] J. Liu, S. Aksoy, N. Scheerbaum, M. Acet, O. Gutfleisch, Appl. Phys. Lett. 95 (2009) 232515. [9] Z. Li, C. Jing, H.L. Zhang, D.H. Yu, L. Chen, B.J. Kang, S.X. Cao, J.C. Zhang, J. Appl. Phys. 108 (2010) 113908. [10] A. Sozinov, A.A. Likhachev, N. Lanska, O. Söderberg, K. Ullakko, V.K. Lindroos, Mater. Sci. Eng., A 378 (2004) 399. [11] J. Liu, N. Scheerbaum, S. Kauffmann-Weiss, O. Gutfleisch, Adv. Eng. Mater. 14 (2012) 653. [12] V.V. Khovaylo, K.P. Skokov, O. Gutfleisch, H. Miki, R. Kainuma, T. Kanomata, Appl. Phys. Lett. 97 (2010) 052503. [13] J. Liu, N. Scheerbaum, J. Lyubina, O. Gutfleisch, Appl. Phys. Lett. 93 (2008) 102512. [14] F.X. Hu, B.G. Shen, J.R. Sun, Z.H. Cheng, G.H. Rao, X.X. Zhang, Appl. Phys. Lett. 78 (2001) 3675. [15] S. Fujieda, A. Fujita, K. Fukamichi, Y. Yamazaki, Y. Iijima, Appl. Phys. Lett. 79 (2001) 653. [16] L. Morellon, P.A. Algarabel, M.R. Ibarra, J. Blasco, B. García-Landa, Z. Arnold, F. Albertini, Phys. Rev. B 58 (1998) R14721. [17] Z. Gercsi, E.K. Delczeg-Czirjak, L. Vitos, A.S. Wills, A. Daoud-Aladine, K.G. Sandeman, Phys. Rev. B 88 (2013) 024417. [18] M.I. Bartashevich, T. Goto, N.V. Baranov, V.S. Gaviko, Physica B 351 (2004) 71. [19] S.C. Ma, D. Hou, Y.Y. Gong, L.Y. Wang, Y.L. Huang, Z.C. Zhong, D.H. Wang, Y.W. Du, Appl. Phys. Lett. 104 (2014) 022410. [20] A. Szytuła, in: K.H.J. Buschow (Ed.), Handbook of Magnetic Materials, vol. 6, Elsevier, Amsterdam, 1991, p. 85. [21] M. Duraj, A. Szytuła, Acta Phys. Pol., A 117 (2010) 603. [22] H. Fujii, T. Okamoto, T. Shigeoka, N. Iwata, Solid State Commun. 53 (1985) 715. [23] P. Kumar, N.K. Singh, K.G. Suresh, A.K. Nigam, S.K. Malik, J. Phys.: Condens. Matter 19 (2007) 386210. [24] E.G. Gerasimov, R.Y. Umetsu, N.V. Mushnikov, A. Fujita, T. Kanomata, J. Phys.: Condens. Matter 19 (2007) 486202. [25] E.G. Gerasimov, V.S. Gaviko, V.N. Neverov, A.V. Korolyov, J. Alloys Comp. 343 (2002) 14. [26] B. Emre, I. Dincer, Y. Elerman, E. Duman, Phys. Scr. 80 (2009) 055703. [27] G. Venturini, R. Welter, E. Ressouche, B. Malaman, J. Alloys Comp. 223 (1995) 101.
150
Y.Y. Gong et al. / Journal of Alloys and Compounds 628 (2015) 146–150
[28] P. Kumar, K.G. Suresh, A.K. Nigam, A. Magnus, A.A. Coelho, S. Gama, Phys. Rev. B 77 (2008) 224427. [29] E.G. Gerasimov, N.V. Mushnikov, Phys. Rev. B 72 (2005) 064446. [30] C.L. Zhang, Y.X. Zheng, H.C. Xuan, S.C. Ma, Q.Q. Cao, D.H. Wang, Y.W. Du, J. Phys. D Appl. Phys. 44 (2011) 135003. [31] G.H. Guo, Y. Wu, H.B. Zhang, D.A. Filippov, R.Z. Levitin, V.V. Snegirev, Chin. Phys. 11 (2002) 608.
[32] A.E. Clark, in: K.H.J. Buschow (Ed.), Handbook of Magnetic Materials, vol. 1, Elsevier, Amsterdam, 1980, p. 531. [33] B.W. Wang, S.L. Tang, X.M. Jin, L.Z. Cheng, K.Y. He, Appl. Phys. Lett. 69 (1996) 3429. [34] L. Xu, C.B. Jiang, H.B. Xu, Appl. Phys. Lett. 89 (2006) 192507. [35] K. Prajapati, A.G. Jenner, M.P. Schulze, R.D. Greenough, J. Appl. Phys. 73 (1993) 6171.