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Enhanced magnetocaloric properties in annealed Heusler Ni–Mn–Sn ribbons
Journal of Magnetism and Magnetic Materials 374 (2015) 153–156
Contents lists available at ScienceDirect
Journal of Magnetism and Magnetic Materials journal homepage: www.elsevier.com/locate/jmmm
Enhanced magnetocaloric properties in annealed Heusler Ni–Mn–Sn ribbons Wu Wang a, Hongwei Li a, Jian Ren a, Jianxun Fu b, Qijie Zhai b, Zhiping Luo c, Hongxing Zheng a,n a
Laboratory for Microstructures, Shanghai University, Shanghai 200072, China Shanghai Key Laboratory of Modern Metallurgy & Materials Processing, Shanghai University, Shanghai 200072, China c Department of Chemistry and Physics, Fayetteville State University, Fayetteville, NC 28301, USA b
art ic l e i nf o
a b s t r a c t
Article history: Received 5 May 2014 Received in revised form 22 July 2014 Available online 21 August 2014
In the present study, annealing effects on the magnetostructural transitions and magnetic properties were investigated based on Heusler Ni49Mn39Sn12 ribbons. Experimental results show that a larger magnetic entropy change is obtained in case of the ribbons annealed at 973 K. The enhancement was explained from the atomic order, thermal hysteresis and sub-grain microstructure. It is proposed that effective annealing occurs around the L21-B2 ordering transition temperature for Heusler Ni–Mn based ribbons. & 2014 Elsevier B.V. All rights reserved.
Keywords: Martensitic transformation Heusler Ni–Mn–Sn materials Atomic order Magnetic entropy change
1. Introduction Heusler Ni–Mn based materials have attracted considerable interest because of their giant magnetocaloric effect (GMCE) originated from the solid-state first-order martensitic transformation, and second-order magnetic transition in austenite [1,2]. Sánchez-Alarcos et al. [3] found both transition temperatures of polycrystalline Ni49.5Mn28.5Ga22 monotonously decreased with increasing the annealing temperature below 1073 K and then slightly increased at 1173 K. Similar result was observed in Ni49.4Mn27.7Ga22.9 single crystal [4]. Ishikawa et al. [5] found that the magnetic transition temperature of Ni2MnGa0.5Al0.5 alloy increased with decreasing the annealing temperature. Wu et al. [6] also proposed both transition temperatures and magnetocaloric effect of Ni–Mn–Sn ribbons closely linked to the atomic order degrees. In case of Ni–Ga–Fe alloy, the martensitic transition would be affected by not only the atomic order but also the magnetic factors [7]. However, both the martensitic and magnetic transition temperatures almost kept constant under various annealing processes due to the absence of L21-B2 ordering transition in Ni49.5Mn37Sn13.5 and Ni49Mn36.5Sb14.5 [8]. Recently, Ray et al. [9] suggested grain size would also play an important
n Correspondence to: Laboratory for Microstructures, Shanghai University, Rixin Building, Room 412, Yanchang Road 149, Shanghai 200072, China. Tel./fax: þ 86 21 56334045/1218. E-mail address: [email protected] (H. Zheng).
http://dx.doi.org/10.1016/j.jmmm.2014.08.042 0304-8853/& 2014 Elsevier B.V. All rights reserved.
role in the transition temperatures besides the atomic order in Ni–Mn–Sb ribbons. On the other hand, previous studies have proven that melt-spinning technique could effectively promote more homogeneous single-phase materials, substantially shortened annealing stage and improved MCE properties [10–12]. However, to the best of our knowledge, limited information on the annealing effect in Heusler Ni–Mn based ribbons was reported. The main objective of the present work is to study the magnetic properties of annealed Ni49Mn39Sn12 ribbons. 2. Experimental procedures An ingot with nominal composition of Ni49Mn39Sn12 (at%) was arc melted from Ni, Mn and Sn with purities of 99.99 wt% in argon gas atmosphere. Additional 5 wt% Mn was added to compensate for evaporation loss. The ingot was melted three times to ensure homogeneity, and then the ribbons were fabricated using meltspinning technique at a linear speed of 10 m/s. The resultant ribbons were 20 mm long, 4–6 mm wide and 30 μm thick. The compositions of the melt-spun ribbons are measured by the chemical method as Ni48.96Mn39.03Sn12.01. The ribbons were sealed in quartz tubes and annealed at 773 K, 973 K and 1173 K, respectively, for 1 h followed by water quenching. Hereinafter the asspun and annealed ribbons were referred as R-as-spun, R-773 K, R-973 K and R-1173 K. Differential scanning calorimetric measurements (DSC, Netzsch DSC 404C and PerkinElmer Diamond DSC) were performed to
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W. Wang et al. / Journal of Magnetism and Magnetic Materials 374 (2015) 153–156
determine the characteristic temperatures of L21-B2 ordering transition and the martensitic transformation at heating/cooling rates of 10 K/min. X-ray diffraction (XRD, D/MAX2200) was conducted to identify the atomic order degree and crystal structures using Cu Kα radiation. Magnetic properties were carried out using physical property measurement systems (Quantum Design PPMS-9) under a magnetic field change up to 18 kOe. Microstructures were observed using a Phenom™ Pro scanning electron microscope.
revealed that higher atomic order degree would result in higher martensitic transition temperatures. Therefore, the atomic order can be characterized by means of the phase transformation temperatures. The DSC measurements reveal that the ribbons possess higher order with elevated annealing temperatures, as
3. Results and discussion Fig. 1 shows the DSC heating curve ranging from 773 K to 1273 K of melt-spun Ni49Mn39Sn12 ribbon. The peak corresponding to the L21-B2 ordering transition occurs at around 900 K, which agrees well with the ternary Ni–Mn–Sn phase diagram [13]. XRD patterns taken from the Ni49Mn39Sn12 ribbons with various annealing temperatures are presented in Fig. 2a. All ribbons are well indexed as cubic L21 austenitic phase [14]. Generally the degree of L21 long-range atomic order can be qualitatively evaluated from the evolution of the intensities of superlattice reflection peaks, such as (111) and (311) [15–17]. However, no clear difference of the intensity ratio of I(111)/I(220) can be distinguished for these four ribbons, which may relate the limited resolution of XRD diffraction compared to power neutron diffraction. Previous investigations in Heusler Ni–Mn–Sn [6] and Ni–Mn–Ga [3,4]
Fig. 1. Differential scanning calorimetric measurement shows the L21-B2 ordering transition of Ni49Mn39Sn12 melt-spun ribbons occurring at around 900 K upon heating.
Fig. 3. Magnetic entropy change around the martensitic transformation and magnetic transition of austenite in Ni49Mn39Sn12 ribbons for a magnetic field change of 18 kOe.
Fig. 4. The thermomagnetic curves of Ni49Mn39Sn12 ribbons in the field of 1 kOe upon heating and cooling.
Fig. 2. X-ray diffraction patterns (a) and differential scanning calorimetric curves and (b) of Ni49Mn39Sn12 ribbons.
W. Wang et al. / Journal of Magnetism and Magnetic Materials 374 (2015) 153–156
155
Fig. 5. Backscattered electron images taken from the free surface of R-973 K (a) and R-1173 K (b).
shown in Fig. 2b. Furthermore, it is noticed that the Mp and Ap values of R-973 K and R-1173 K are almost equal, indicating very close high atomic order degrees for these two ribbons. While for the R-as-spun and R-773 K, both possess lower atomic orders. The magnetic entropy change, ΔSM, as a function of temperature RH is calculated using the Maxwell relation ΔSM ¼ 0 ð∂M=∂TÞdH based on the isothermal magnetization curves (not shown here), as shown in Fig. 3. The large positive peaks correspond to the martensitic transformation, while the small negative peaks are resulted from the magnetic transition of austenite. It is clear that high atomic degree favors improved magnetic entropy change. The ΔSM peak values around the martensitic transition are 2.6 J kg 1 K 1 for R-asspun, 2.3 J kg 1 K 1 for R-773 K, 8.2 J kg 1 K 1 for R-973 K and 6.2 J kg 1 K 1 for R-1173 K, under a magnetic field change of 1.8 T. It is interesting that the magnetic entropy change of R-973 K improved about 30% over R-1173 K. Similar phenomena occur for the magnetic transition of austenite, although both ribbons possess similar atomic order degree as discussed above. In the present study, we proposed that the enhancement should be ascribed to smaller thermal hysteresis and sub-grain microstructure besides the higher atomic order degree. Fig. 4 shows the thermomagnetic curves of Ni49Mn39Sn12 ribbons in the magnetic field of 1 kOe upon heating and cooling. The austenite start and finish temperatures (As and Af), martensite start and finish temperatures (Ms and Mf) and the Curie temperature of the austenite T AC can be determined, as shown in the example of R-1173 K. All ribbons show similar temperature dependence of the magnetization. Upon cooling, magnetization initially stabilizes, and then increases dramatically due to the paramagnetic to ferromagnetic transition of austenite. Further cooling below Ms, a sharp drop of magnetization occurs and reaches the minimum associated with the first-order martensitic transition from ferromagnetic austenite to weak magnetic martensite. During further cooling, the martensite undergoes a magnetic transition from weak magnetic to ferromagnetic [6]. It is completely reversible for the magnetization change upon heating. It should be noticed the thermal hysteresis ΔT(As–Mf) in a magnetic field of 1 kOe decreases for R-as-spun (20 K), R-773 K (16.8 K) and R-973 K (8.5 K), and then increases slightly for R-1173 K (10.5 K). It has been suggested that the thermal hysteresis originates from the friction of phase boundary motion [18], and sharp thermal hysteresis implies that less energy is needed for the magnetic-induced phase boundary motion. On the other hand, Fig. 5 shows the backscattered electron images taken from the free surface of R-973 K and R-1173 K. A lot of sub-grains in R-973 K are still visible, which are apparently different from the large grain
microstructure in R-1173 K. Sub-grains would exert pressure to the adjacent grains in the inner part of the grains due to the cell contraction during the phase transition [19], and thus lower the activation energy [20]. Moreover, it is reasonable that sub-grain boundaries would store more energy and release during the martensitic transition process [21], and therefore enhance the magnetic entropy change.
4. Conclusions In summary, we investigated the effect of annealing temperature for the Ni49Mn39Sn12 ribbons and obtained the following conclusions. The L21-B2 ordering transition of Ni49Mn39Sn12 ribbons takes place at around 900 K. High temperature annealing is favorable to obtain high atomic order degree. Larger ΔSM in R-973 K is associated with higher atomic order degree, smaller thermal hysteresis and sub-grain microstructure.
Acknowledgments The authors gratefully acknowledge the support from the National Natural Science Foundation of China (51474144, 51201096), the Specialized Research Fund for the Doctoral Program of Higher Education of China (20123108120019), and the Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry. References [1] T. Krenke, E. Duman, M. Acet, E.F. Wassermann, X. Moya, L.I. Mañosa, A. Planes, Nat. Mater. 4 (2005) 450–454. [2] H.X. Zheng, W. Wang, S.C. Xue, Q.J. Zhai, J. Frenzel, Z.P. Luo, Acta Mater. 61 (12) (2013) 4648–4656. [3] V. Sánchez-Alarcos, V. Recarte, J.I. Pérez-Landazábal, G.J. Cuello, Acta Mater. 55 (2007) 3883–3889. [4] V. Sánchez-Alarcos, J.I. Pérez-Landazábal, V. Recarte, J.A. RodríguezVelamazán, V.A. Chernenko, J. Phys.: Condens. Matter 22 (2010) 166001. [5] H. Ishikawa, R.Y. Umetsu, K. Kobayashi, A. Fujita, R. Kainuma, K. Ishida, Acta Mater. 56 (2008) 4789–4797. [6] D.Z. Wu, S.C. Xue, J. Frenzel, G. Eggeler, Q.J. Zhai, H.X. Zheng, Mater. Sci. Eng. A 534 (2012) 568–572. [7] K. Oikawa, T. Omori, R. Kainuma, K. Ishida, J. Magn. Magn. Mater. 272–276 (2004) 2043–2044. [8] V. Sánchez-Alarcos, J.I. Pérez-Landazábal, V. Recarte, I. Lucia, J. Vélez, J.A. Rodríguez-Velamazán, Acta Mater. 61 (2013) 4676–4682. [9] M.K. Ray, K. Bagani, R.K. Singh, B. Majumdar, S. Banerjee, J. Appl. Phys. 114 (2013) 123904.
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[10] J.D. Santos, T. Sanchez, P. Alvarez, M.L. Sanchez, J.L. Sánchez Llamazares, J. Appl. Phys. 103 (2008) 07B326. [11] J. Liu, N. Scheerbaum, D. Hinz, O. Gutfleisch, Appl. Phys. Lett. 92 (2008) 162509. [12] H.C. Xuan, K.X. Xie, D.H. Wang, Z.D. Han, C.L. Zhang, B.X. Gu, Y.W. Du, Appl. Phys. Lett. 92 (2008) 242506. [13] E. Watchel, F. Henninger, B. Predel, J. Magn. Magn. Mater. 38 (1983) 305–315. [14] T. Krenke, M. Acet, E.F. Wassermann, X. Moya, L. Mañosa, A. Planes, Phys. Rev. B 72 (2005) 014412. [15] C. Seguí, J. Pons, E. Cesari, Acta Mater. 55 (2007) 1649–1655.
[16] Y. Takamura, R. Nakane, S. Sugahara, J. Appl. Phys. 105 (2009) 07B109. [17] Z.P. Luo, Y. Vasquez, J.F. Bondi, R.E. Schaak, Ultramicroscopy 111 (2011) 1295–1304. [18] W.H. Wang, J.L. Chen, Z.H. Liu, G.H. Wu, W.S. Zhan, Phys. Rev. B 65 (2001) 012416. [19] W.B. Cui, X.K. Lv, F. Yang, Y. Yu, R. Skomski, X.G. Zhao, W. Liu, Z.D. Zhang, J. Appl. Phys. 107 (2010) 09A938. [20] L. Lu, M.O. Lai, S. Zhang., J. Mater. Process. Technol. 63 (2005) 100–104. [21] S.H. Choi, Y.S. Jin, Mater. Sci. Eng. A. 371 (2004) 149–159.
Contents lists available at ScienceDirect
Journal of Magnetism and Magnetic Materials journal homepage: www.elsevier.com/locate/jmmm
Enhanced magnetocaloric properties in annealed Heusler Ni–Mn–Sn ribbons Wu Wang a, Hongwei Li a, Jian Ren a, Jianxun Fu b, Qijie Zhai b, Zhiping Luo c, Hongxing Zheng a,n a
Laboratory for Microstructures, Shanghai University, Shanghai 200072, China Shanghai Key Laboratory of Modern Metallurgy & Materials Processing, Shanghai University, Shanghai 200072, China c Department of Chemistry and Physics, Fayetteville State University, Fayetteville, NC 28301, USA b
art ic l e i nf o
a b s t r a c t
Article history: Received 5 May 2014 Received in revised form 22 July 2014 Available online 21 August 2014
In the present study, annealing effects on the magnetostructural transitions and magnetic properties were investigated based on Heusler Ni49Mn39Sn12 ribbons. Experimental results show that a larger magnetic entropy change is obtained in case of the ribbons annealed at 973 K. The enhancement was explained from the atomic order, thermal hysteresis and sub-grain microstructure. It is proposed that effective annealing occurs around the L21-B2 ordering transition temperature for Heusler Ni–Mn based ribbons. & 2014 Elsevier B.V. All rights reserved.
Keywords: Martensitic transformation Heusler Ni–Mn–Sn materials Atomic order Magnetic entropy change
1. Introduction Heusler Ni–Mn based materials have attracted considerable interest because of their giant magnetocaloric effect (GMCE) originated from the solid-state first-order martensitic transformation, and second-order magnetic transition in austenite [1,2]. Sánchez-Alarcos et al. [3] found both transition temperatures of polycrystalline Ni49.5Mn28.5Ga22 monotonously decreased with increasing the annealing temperature below 1073 K and then slightly increased at 1173 K. Similar result was observed in Ni49.4Mn27.7Ga22.9 single crystal [4]. Ishikawa et al. [5] found that the magnetic transition temperature of Ni2MnGa0.5Al0.5 alloy increased with decreasing the annealing temperature. Wu et al. [6] also proposed both transition temperatures and magnetocaloric effect of Ni–Mn–Sn ribbons closely linked to the atomic order degrees. In case of Ni–Ga–Fe alloy, the martensitic transition would be affected by not only the atomic order but also the magnetic factors [7]. However, both the martensitic and magnetic transition temperatures almost kept constant under various annealing processes due to the absence of L21-B2 ordering transition in Ni49.5Mn37Sn13.5 and Ni49Mn36.5Sb14.5 [8]. Recently, Ray et al. [9] suggested grain size would also play an important
n Correspondence to: Laboratory for Microstructures, Shanghai University, Rixin Building, Room 412, Yanchang Road 149, Shanghai 200072, China. Tel./fax: þ 86 21 56334045/1218. E-mail address: [email protected] (H. Zheng).
http://dx.doi.org/10.1016/j.jmmm.2014.08.042 0304-8853/& 2014 Elsevier B.V. All rights reserved.
role in the transition temperatures besides the atomic order in Ni–Mn–Sb ribbons. On the other hand, previous studies have proven that melt-spinning technique could effectively promote more homogeneous single-phase materials, substantially shortened annealing stage and improved MCE properties [10–12]. However, to the best of our knowledge, limited information on the annealing effect in Heusler Ni–Mn based ribbons was reported. The main objective of the present work is to study the magnetic properties of annealed Ni49Mn39Sn12 ribbons. 2. Experimental procedures An ingot with nominal composition of Ni49Mn39Sn12 (at%) was arc melted from Ni, Mn and Sn with purities of 99.99 wt% in argon gas atmosphere. Additional 5 wt% Mn was added to compensate for evaporation loss. The ingot was melted three times to ensure homogeneity, and then the ribbons were fabricated using meltspinning technique at a linear speed of 10 m/s. The resultant ribbons were 20 mm long, 4–6 mm wide and 30 μm thick. The compositions of the melt-spun ribbons are measured by the chemical method as Ni48.96Mn39.03Sn12.01. The ribbons were sealed in quartz tubes and annealed at 773 K, 973 K and 1173 K, respectively, for 1 h followed by water quenching. Hereinafter the asspun and annealed ribbons were referred as R-as-spun, R-773 K, R-973 K and R-1173 K. Differential scanning calorimetric measurements (DSC, Netzsch DSC 404C and PerkinElmer Diamond DSC) were performed to
154
W. Wang et al. / Journal of Magnetism and Magnetic Materials 374 (2015) 153–156
determine the characteristic temperatures of L21-B2 ordering transition and the martensitic transformation at heating/cooling rates of 10 K/min. X-ray diffraction (XRD, D/MAX2200) was conducted to identify the atomic order degree and crystal structures using Cu Kα radiation. Magnetic properties were carried out using physical property measurement systems (Quantum Design PPMS-9) under a magnetic field change up to 18 kOe. Microstructures were observed using a Phenom™ Pro scanning electron microscope.
revealed that higher atomic order degree would result in higher martensitic transition temperatures. Therefore, the atomic order can be characterized by means of the phase transformation temperatures. The DSC measurements reveal that the ribbons possess higher order with elevated annealing temperatures, as
3. Results and discussion Fig. 1 shows the DSC heating curve ranging from 773 K to 1273 K of melt-spun Ni49Mn39Sn12 ribbon. The peak corresponding to the L21-B2 ordering transition occurs at around 900 K, which agrees well with the ternary Ni–Mn–Sn phase diagram [13]. XRD patterns taken from the Ni49Mn39Sn12 ribbons with various annealing temperatures are presented in Fig. 2a. All ribbons are well indexed as cubic L21 austenitic phase [14]. Generally the degree of L21 long-range atomic order can be qualitatively evaluated from the evolution of the intensities of superlattice reflection peaks, such as (111) and (311) [15–17]. However, no clear difference of the intensity ratio of I(111)/I(220) can be distinguished for these four ribbons, which may relate the limited resolution of XRD diffraction compared to power neutron diffraction. Previous investigations in Heusler Ni–Mn–Sn [6] and Ni–Mn–Ga [3,4]
Fig. 1. Differential scanning calorimetric measurement shows the L21-B2 ordering transition of Ni49Mn39Sn12 melt-spun ribbons occurring at around 900 K upon heating.
Fig. 3. Magnetic entropy change around the martensitic transformation and magnetic transition of austenite in Ni49Mn39Sn12 ribbons for a magnetic field change of 18 kOe.
Fig. 4. The thermomagnetic curves of Ni49Mn39Sn12 ribbons in the field of 1 kOe upon heating and cooling.
Fig. 2. X-ray diffraction patterns (a) and differential scanning calorimetric curves and (b) of Ni49Mn39Sn12 ribbons.
W. Wang et al. / Journal of Magnetism and Magnetic Materials 374 (2015) 153–156
155
Fig. 5. Backscattered electron images taken from the free surface of R-973 K (a) and R-1173 K (b).
shown in Fig. 2b. Furthermore, it is noticed that the Mp and Ap values of R-973 K and R-1173 K are almost equal, indicating very close high atomic order degrees for these two ribbons. While for the R-as-spun and R-773 K, both possess lower atomic orders. The magnetic entropy change, ΔSM, as a function of temperature RH is calculated using the Maxwell relation ΔSM ¼ 0 ð∂M=∂TÞdH based on the isothermal magnetization curves (not shown here), as shown in Fig. 3. The large positive peaks correspond to the martensitic transformation, while the small negative peaks are resulted from the magnetic transition of austenite. It is clear that high atomic degree favors improved magnetic entropy change. The ΔSM peak values around the martensitic transition are 2.6 J kg 1 K 1 for R-asspun, 2.3 J kg 1 K 1 for R-773 K, 8.2 J kg 1 K 1 for R-973 K and 6.2 J kg 1 K 1 for R-1173 K, under a magnetic field change of 1.8 T. It is interesting that the magnetic entropy change of R-973 K improved about 30% over R-1173 K. Similar phenomena occur for the magnetic transition of austenite, although both ribbons possess similar atomic order degree as discussed above. In the present study, we proposed that the enhancement should be ascribed to smaller thermal hysteresis and sub-grain microstructure besides the higher atomic order degree. Fig. 4 shows the thermomagnetic curves of Ni49Mn39Sn12 ribbons in the magnetic field of 1 kOe upon heating and cooling. The austenite start and finish temperatures (As and Af), martensite start and finish temperatures (Ms and Mf) and the Curie temperature of the austenite T AC can be determined, as shown in the example of R-1173 K. All ribbons show similar temperature dependence of the magnetization. Upon cooling, magnetization initially stabilizes, and then increases dramatically due to the paramagnetic to ferromagnetic transition of austenite. Further cooling below Ms, a sharp drop of magnetization occurs and reaches the minimum associated with the first-order martensitic transition from ferromagnetic austenite to weak magnetic martensite. During further cooling, the martensite undergoes a magnetic transition from weak magnetic to ferromagnetic [6]. It is completely reversible for the magnetization change upon heating. It should be noticed the thermal hysteresis ΔT(As–Mf) in a magnetic field of 1 kOe decreases for R-as-spun (20 K), R-773 K (16.8 K) and R-973 K (8.5 K), and then increases slightly for R-1173 K (10.5 K). It has been suggested that the thermal hysteresis originates from the friction of phase boundary motion [18], and sharp thermal hysteresis implies that less energy is needed for the magnetic-induced phase boundary motion. On the other hand, Fig. 5 shows the backscattered electron images taken from the free surface of R-973 K and R-1173 K. A lot of sub-grains in R-973 K are still visible, which are apparently different from the large grain
microstructure in R-1173 K. Sub-grains would exert pressure to the adjacent grains in the inner part of the grains due to the cell contraction during the phase transition [19], and thus lower the activation energy [20]. Moreover, it is reasonable that sub-grain boundaries would store more energy and release during the martensitic transition process [21], and therefore enhance the magnetic entropy change.
4. Conclusions In summary, we investigated the effect of annealing temperature for the Ni49Mn39Sn12 ribbons and obtained the following conclusions. The L21-B2 ordering transition of Ni49Mn39Sn12 ribbons takes place at around 900 K. High temperature annealing is favorable to obtain high atomic order degree. Larger ΔSM in R-973 K is associated with higher atomic order degree, smaller thermal hysteresis and sub-grain microstructure.
Acknowledgments The authors gratefully acknowledge the support from the National Natural Science Foundation of China (51474144, 51201096), the Specialized Research Fund for the Doctoral Program of Higher Education of China (20123108120019), and the Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry. References [1] T. Krenke, E. Duman, M. Acet, E.F. Wassermann, X. Moya, L.I. Mañosa, A. Planes, Nat. Mater. 4 (2005) 450–454. [2] H.X. Zheng, W. Wang, S.C. Xue, Q.J. Zhai, J. Frenzel, Z.P. Luo, Acta Mater. 61 (12) (2013) 4648–4656. [3] V. Sánchez-Alarcos, V. Recarte, J.I. Pérez-Landazábal, G.J. Cuello, Acta Mater. 55 (2007) 3883–3889. [4] V. Sánchez-Alarcos, J.I. Pérez-Landazábal, V. Recarte, J.A. RodríguezVelamazán, V.A. Chernenko, J. Phys.: Condens. Matter 22 (2010) 166001. [5] H. Ishikawa, R.Y. Umetsu, K. Kobayashi, A. Fujita, R. Kainuma, K. Ishida, Acta Mater. 56 (2008) 4789–4797. [6] D.Z. Wu, S.C. Xue, J. Frenzel, G. Eggeler, Q.J. Zhai, H.X. Zheng, Mater. Sci. Eng. A 534 (2012) 568–572. [7] K. Oikawa, T. Omori, R. Kainuma, K. Ishida, J. Magn. Magn. Mater. 272–276 (2004) 2043–2044. [8] V. Sánchez-Alarcos, J.I. Pérez-Landazábal, V. Recarte, I. Lucia, J. Vélez, J.A. Rodríguez-Velamazán, Acta Mater. 61 (2013) 4676–4682. [9] M.K. Ray, K. Bagani, R.K. Singh, B. Majumdar, S. Banerjee, J. Appl. Phys. 114 (2013) 123904.
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[10] J.D. Santos, T. Sanchez, P. Alvarez, M.L. Sanchez, J.L. Sánchez Llamazares, J. Appl. Phys. 103 (2008) 07B326. [11] J. Liu, N. Scheerbaum, D. Hinz, O. Gutfleisch, Appl. Phys. Lett. 92 (2008) 162509. [12] H.C. Xuan, K.X. Xie, D.H. Wang, Z.D. Han, C.L. Zhang, B.X. Gu, Y.W. Du, Appl. Phys. Lett. 92 (2008) 242506. [13] E. Watchel, F. Henninger, B. Predel, J. Magn. Magn. Mater. 38 (1983) 305–315. [14] T. Krenke, M. Acet, E.F. Wassermann, X. Moya, L. Mañosa, A. Planes, Phys. Rev. B 72 (2005) 014412. [15] C. Seguí, J. Pons, E. Cesari, Acta Mater. 55 (2007) 1649–1655.
[16] Y. Takamura, R. Nakane, S. Sugahara, J. Appl. Phys. 105 (2009) 07B109. [17] Z.P. Luo, Y. Vasquez, J.F. Bondi, R.E. Schaak, Ultramicroscopy 111 (2011) 1295–1304. [18] W.H. Wang, J.L. Chen, Z.H. Liu, G.H. Wu, W.S. Zhan, Phys. Rev. B 65 (2001) 012416. [19] W.B. Cui, X.K. Lv, F. Yang, Y. Yu, R. Skomski, X.G. Zhao, W. Liu, Z.D. Zhang, J. Appl. Phys. 107 (2010) 09A938. [20] L. Lu, M.O. Lai, S. Zhang., J. Mater. Process. Technol. 63 (2005) 100–104. [21] S.H. Choi, Y.S. Jin, Mater. Sci. Eng. A. 371 (2004) 149–159.