- Email: [email protected]
The magnetism and electronic transport properties of Mn3Sn1−xSixC
Journal of Magnetism and Magnetic Materials 391 (2015) 22–25
Contents lists available at ScienceDirect
Journal of Magnetism and Magnetic Materials journal homepage: www.elsevier.com/locate/jmmm
The magnetism and electronic transport properties of Mn3Sn1 xSixC Yongchun Wen b, Cong Wang a,n, Man Nie a, Ying Sun a,b a b
Center of Condensed Matter and Materials Physics, Department of Physics, Beihang University, Beijing 100191, People's Republic of China School of Materials Engineering, YanCheng Institute of Technology, YanCheng 224051, People's Republic of China
art ic l e i nf o
a b s t r a c t
Article history: Received 6 May 2013 Received in revised form 13 April 2015 Accepted 27 April 2015 Available online 28 April 2015
The lattice, magnetic and electronic transport properties of the compounds Mn3Sn1 xSixC (0 r x r0.4) are investigated. The results have shown that Si-doping in the antiperovskite Mn3SnC induces the decrease of the nearest neighbouring Mn–Mn bond distance of Mn3Sn1 xSixC, and the magnetic structure transforms from ferrimagnetic to antiferromagnetic when x Z0.2. With the increase of Si, the Neel temperature TN rises. The TN of Mn3Sn1 xSixC(x ¼0.2, 0.3, 0.4) are 217 K, 257 K and 290 K, respectively. However, the magnetovolume effect is quenched. In Mn3SnC and Mn3Sn1 xSixC (x ¼0.2, 0.3, 0.4) compounds, there exists an anomalous increase in resistivity at a certain temperature that coincides well with their Curie temperature TC or Neel temperature TN. The temperature dependence of the resistivity of Mn3Sn1 xSixC (x ¼0, 0.2, 0.3, 0.4) exhibits semiconducting-like behavior at low temperature and metallic-like behavior at high temperature. & 2015 Published by Elsevier B.V.
Keywords: Antiperovskite structure Mn3Sn1 xSixC Electronic transport
1. Introduction Antiperovskite manganese compounds Mn3AX (A¼Sn, Ga, Zn, and Ni, etc. X ¼carbon or nitrogen), in which the Mn atoms are located on the face centered positions, the A atoms on the cubic corners, and the non-metal X atom at the body centered position in a cubic lattice, are well known for a couple of years [1]. These compounds show a wide variety of interesting physical phenomena such as superconductivity, magnetoresistivity, and a nearly zero temperature coefficient of resistivity [2–5]. In particular, the antiperovskite manganese compounds exhibit intriguing magnetic structure, and show abundant magnetic transition, abnormal transport and lattice variation [6–9]. Therefore, these compounds have attracted great attentions in recent years [10–15]. Antiperovskite structured Mn3SnC has a cubic crystal structure with space group Pm3¯ m. In spite of the simple crystal structure, Mn3SnC possesses a complicated spin arrangement of noncollinear ferrimagnetic (FI) state, consisting of an antiferromagnetic (AFM) and ferromagnetic (FM) sublattices, exiting up to the Curie temperature TC, 265 K [6]. The magnetic structure is non-collinear: the magnetic moments at MnI and MnII sites in Fig.1 have a ‘square configuration’ with μ(MnI)¼ μ(MnII)¼ 2.4 μB and a ferromagnetic component of 0.2 μB along the [001] direction on each of these sites. The magnetic moments on MnIII sites align ferromagnetically with μ(MnIII)¼ 0.65 μB along the [001] direction [6]. The results by n
Corresponding author. E-mail address: [email protected] (C. Wang).
http://dx.doi.org/10.1016/j.jmmm.2015.04.111 0304-8853/& 2015 Published by Elsevier B.V.
neutron diffraction showed that the magnetic moments of Mn atoms are much smaller than 4 μB observed in other ordered manganese alloys [8], indicating a strong itinerant characteristic of d electrons in the Mn atoms in Mn3SnC. With increasing temperature, the transition from ferrimagnetic (FI) to the paramagnetic (PM) state is accompanied by an abrupt contraction of the lattice without change of the type of the crystal structure, i.e. a negative thermal expansion (NTE) behavior occurs. Meanwhile, an abnormal change of resistivity exist in the material. In our another anti-perovskite manganese nitride Mn3Zn1 xGexN, the starting temperature point and range where the NTE appeared were increased by Ge-doping [7,10], which are beneficial to the applications of NTE materials. In order to further reveal the effects of doped elements on the lattice, magnetic and electronic transport properties and try to develop new applicable materials, Mn3Sn1 xSixC compounds are investigated in this paper.
2. Experimental details The samples Mn3Sn1 xSixC (x ¼0, 0.1, 0.2, 0.3, 0.4) were prepared using manganese, tin, silicon, and graphite powders with purity 99.95% as the starting powder materials. They were mixed in the stoichiometric proportion and pressed into pellets. The pellets were wrapped by tantalum foil, and then placed in an evacuated quartz tube. The samples were sintered in a box furnace at 800 °C for 5 days, then cooled down to room temperature. X-ray diffraction patterns at room temperature were collected
Y. Wen et al. / Journal of Magnetism and Magnetic Materials 391 (2015) 22–25
23
Fig. 3. Variation of the lattice constant of Mn3Sn1 xSixC (x ¼ 0, 0.1, 0.2, 0.3, 0.4) with increasing Si-doped content x.
Fig. 1. The antiperovskite structure and magnetic structure of Mn3SnC. The section z ¼1/2 shows the antiferromagnetic square arrangement of MnI and MnII atoms.
Fig. 4. Temperature dependence of the resistivity (rectangles) and the susceptibility (triangles) of the Mn3SnC compound. The arrow indicates the Curie temperature Tc.
3. Results and discussion
Fig. 2. X-ray diffraction patterns of the Mn3Sn1 xSixC compounds.
in a Rigaku D/MAX 2200PC diffractometer using Cu Kα radiation. Software named Powder X [9] was used for indexing and lattice constant calculation. For the measurement of coefficient of thermal expansion (CTE), variable temperature X-ray diffraction from 150 K to 325 K was used to measure the variation of lattice constant on an X’Pert PRO MPD diffractometer. Magnetic susceptibility was measured by a physical property measurement system (PPMS) from 100 K to 350 K at 50 Oe magnetic field. Electrical resistivity measurements (100–300 K) were accomplished using the standard four-probe technique.
Fig. 2 shows the XRD patterns of the Mn3Sn1 xSixC (x ¼0, 0.1, 0.2, 0.3, 0.4) samples that pure antiperovskite cubic structure was formed for these samples. All of the space groups of Mn3Sn1 xSixC are Pm3¯ m, and their lattice parameters are 3.9916 Å, 3.9850 Å, 3.9773 Å, 3.9709 Å, and 3.9655 Å for x ¼0, 0.1, 0.2, 0.3, 0.4, respectively. The lattice constant of Mn3Sn1 xSixC linearly decreases with the increase of x (seen in Fig. 3.), which indicates that Sn is really substituted by Si since the atomic radius of Si (1.32 Å) is smaller than the one of Sn (1.62 Å). The temperature dependence of the resistivity and susceptibility of Mn3SnC is shown in Fig. 4. With increasing temperature, the transition from ferrimagnetic (FI) to the paramagnetic (PM) state takes place. The susceptibility slowly decreases from 150 K to 250 K, and then rapidly drops from 250 K to 280 K. The variation of resistivity with temperature displays metallic-type at low temperatures (T o165 K), and changes into semiconducting-type in the range of 165–269 K. Evidently, the two curves indicate that with decreasing temperature, there exists an anomalous increase in resistivity at 272 K which is in good agreement with their Curie temperature 275 K (i.e., the transition temperature TPM-FI). Namely, the abnormal electronic transport behavior originates from a
24
Fig. 5. Temperature dependence Mn3Sn1 xSixC compounds at 50 Oe.
Y. Wen et al. / Journal of Magnetism and Magnetic Materials 391 (2015) 22–25
of
the
magnetic
susceptibility
of
the
transition from the PM state to the FI state. Fig. 5 presents the temperature dependence of the magnetization for Mn3Sn0.8Si0.2C, Mn3Sn0.7Si0.3C and Mn3Sn0.6Si0.4C compounds. The overall behaviors of the magnetic susceptibility for the three samples display an AFM transition, and the Neel points (TN) are 217 K, 257 K and 289 K, respectively. Namely, the Si-doping changes the magnetic phase transition. It may be that dopingSi makes the Mn–C octahedron distort, and further changes the Mn–Mn exchange integral. For Mn3SnC, the transition from ferrimagnetic (FI) to the paramagnetic (PM) state is accompanied by an abrupt contraction of the lattice without change of the type of the crystal structure [6,16], i.e. a negative thermal expansion (NTE) behavior exists. The abnormal change of the lattice constant with the coefficient of thermal expansion (CTE) αl ¼ 38 10 6 K 1 is observed at about 200–250 K (ΔT ¼50 K) for Mn3SnC. However, The NTE behavior disappears in Mn3Sn0.8Si0.2C, Mn3Sn0.7Si0.3C and Mn3Sn0.6Si0.4C. The CTEs are 9.7 10 6 K 1 (T o213 K), 20 10 6 K 1 (T4 213 K) for Mn3Sn0.8Si0.2C, 5.1 10 6 K 1 (T o255 K), 15 10 6 K 1 (T 4255 K) for Mn3Sn0.8Si0.2C and 3.6 10 6 K 1 (T o283 K), 17 10 6 K 1 (T 4283 K) for Mn3Sn0.6Si0.4C. The temperature dependence of the lattice constant for Mn3Sn1 xSixC (x ¼0, 0.1, 0.2, 0.3, 0.4) is shown in Fig. 7. A series of Mn3Sn1 xSixC remains cubic structure over a whole temperature range. There is a small discontinuous point nearly corresponding to the TN. Owing to the magnetovolume effect (MVE) [17], the spontaneous magnetization in Mn3Sn1 xSixC changes the magnetic atomic distance, and then induces the change of lattice volume, which counteracts the normal thermal expansion. According to Landau theory, the relative volume expansion ωs (ΔV/V) due to MVE is proportional to magnetoelastic coefficients C and the square of spontaneous magnetization Ms2, i.e. ωs ∝ CMs2. For most solid materials, the magnetoelastic coefficient C is very low and the ωs is quite small, and so these materials expand when heating due to the asymmetry of the closest atomic potential well. However, we speculate that the ωs of Mn3SnC is rather big, and its C is also big. With decreasing temperature, the occurrence of ωs near the Curie temperature TC makes the lattice volume enlarge, then results in negative CTE. Sidoping in Mn3SnC may decrease magnetoelastic coefficient C, the MVE gets smaller, and therefore the CTE becomes positive for Mn3Sn0.8Si0.2C and Mn3Sn0.6Si0.4C. However the thermal expansion curves of the two compounds display discontinuous points, which indicates that the MVE still exists. Fig. 8 shows the temperature dependence of the resistivity for Mn3Sn0.9Si0.1C, Mn3Sn0.8Si0.2C, Mn3Sn0.7Si0.3C and Mn3Sn0.6Si0.4C.
Fig. 6. With cubic perovskite symmetry and wave-vector k¼ [000] the group theoretical analysis permits: Γ4g (a) and Γ5g (b) two triangular antiferromagnetic atoms are drawn in the cubic unit-cell.
Y. Wen et al. / Journal of Magnetism and Magnetic Materials 391 (2015) 22–25
25
4. Conclusion
Fig. 7. Temperature dependence of the lattice constants for Mn3Sn1 xSixC.
With introducing the element Si in the antiperovskite structured Mn3SnC, the Mn–Mn distance of Mn3Sn1 xSixC decreases, the magnetic structure changes from FI into AFM when xZ 0.2. When the Si content increases, the negative thermal expansion effect gradually disappears. For Mn3SnC and Mn3Sn1 xSixC (x¼ 0.2, 0.3, 0.4) compounds, there exists an anomalous increase in resistivity at a certain temperature that is in agreement with their Curie temperature TC or Neel temperature TN. The temperature dependence of the resistivity of Mn3Sn1 xSixC (x ¼0, 0.2, 0.3, 0.4) shows semiconducting-type behavior at low temperature and metallic-type behavior at high temperature. Since the Fermi level lies just above a sharp peak of the DOS for Mn3Sn1 xSixC (x ¼0, 0.2, 0.3, 0.4), a shift of the Fermi energy surface probably due to spin polarization can result in an abrupt decrease of the DOS near the Fermi level, which could lead to a pronounced decrease of the effective number of conduction electrons. Correspondingly, the resistivity is enhanced significantly at the transition temperature (Fig. 6).
Acknowledgments This work is supported by National Natural Science Foundation of China (NSFC) (Nos. 51172012, 91122026, and 51472017). We are also grateful to the key laboratory for Ecological–environment Materials of Jiangsu Province and the Natural Science Foundation of China (No: 51402251).
References
Fig. 8. Temperature dependence of the resistivity for Mn3Sn1 xSixC.
For the three compounds, the similar variation of resistivity shows semiconductor-like behavior at low temperature and a metalliclike behavior at high temperature. With increasing temperature, there is obvious change in the transport behavior from semiconducting-type to metal-type at about 225 K, 250 K and 290 K, for Mn3Sn0.8Si0.2C, Mn3Sn0.7Si0.3C and Mn3Sn0.6Si0.4C, respectively. These transition temperatures are in agreement with their Neel temperature TN. Namely, these anomalous behaviors originate from a transition from the paramagnetic state to the antiferromagnetic state. As reported early [8], the 1st principle calculation for Mn3SnC showed that the Fermi energy level located in a sharp peak of the DOS curve. This implies that a small shift of the Fermi energy surface can result in an abrupt decrease of the DOS near the Fermi energy level, which could lead to a pronounced decrease of the effective number of conduction electrons. Correspondingly, the resistivity could be enhanced significantly at the transition temperature for Mn3SnC. However the increasing degree slows down with increasing Si-doping in Mn3Sn0.8Si0.2C, Mn3Sn0.7Si0.3C and Mn3Sn0.6Si0.4C. The Si-doping slightly changes the structure of energy band, but the basic trend of the resistivity is not changed largely.
[1] E.F. Bertaut, D. Fruchart, J.P. Bouchaud, R. Fruchart, Solid State Commun. 6 (1968) 251. [2] R. Prozorov, A. Snezhko, T. He, R.J. Cava, Phys. Rev. B 68 (2003) 180502. [3] A.F. Dong, G.C. Che, W.W. Huang, S.L. Jia, H. Chen, Z.X. Zhao, Physica C 422 (2005) 65. [4] K. Kamishima, T. Goto, H. Nakagawa, N. Miura, M. Ohashi, N. Mori, T. Sasaki, T. Kanomata, Phys. Rev. B 63 (2000) 024426. [5] E.O. Chi., S. Kim, N.H. Hur, Solid State Commun. 120 (2001) 307. [6] D. Fruchart, E.F. Bertaut, J. Phys. Soc. Jpn. 44 (1978) 781. [7] Cong Ying Sun, Yongchun Wang, Wen, Kaigui Zhu, Appl. Phys. Lett. 91 (2007) 231913. [8] K. Motizuki, H. Nagai, J. Phys. C 21 (1988) 5251. [9] K. Takenaka, H. Takagi, Zero thermal expansion in a pure-form antiperovskite manganese nitride, Appl. Phys. Lett. 94 (13) (2009) 131904. [10] Lihua Cong Wang, Qingrong Chu, Ying Yao, Meimei Sun, Lei Wu, Jun Ding, Yuanyuan Yan, Weihua Na, Guannan Tang, Qingzhen Li, Huang, Jeffrey Lynn, Tuning the range, magnitude, and sign of the thermal expansion in intermetallic Mn3(Zn, M)xN(M ¼Ag, Ge), Phys. Rev. B 85 (2012) 220103. [11] Wen Yongchun Sun Ying, Chu Lihua, Nie man, Wang Cong, Abnormal thermal expansion in anti-perovskite magnanese intride, J. Chin. Ceram. Soc. 37 (2009) 73. [12] Lei Ding, Cong Wang, Lihua Chu, Jun Yan, Yuanyuan Na, Qingzhen Huang, Xiaolong Chen, Near zero temperature coefficient of resistivity in antiperovskite Mn3Ni1 xCuxN, Appl. Phys. Lett. 99 (25) (2011) 251905. [13] Cong Ying Sun, Lihua Wang, Yongchun Chu, Man Wen, Nie, Fusheng Liu, Low temperature coefficient of resistivity induced by magnetic transition and lattice contraction in Mn3NiN compound, Scr. Mater. 62 (9) (2010) 686. [14] Cong Lihua Chu, Jun Wang, Yuanyuan Yan, Lei Na, Ying Ding, Sun, Yongchun Wen, Magnetic transition, lattice variation and electronic transport properties of Ag-doped Mn3Ni1 xAgxN antiperovskite compounds, Scr. Mater. 67 (2) (2012) 173. [15] K. Takenaka, A. Ozawa, T. Shibayama, N. Kaneko, T. Oe, C. Urano, Extremely low temperature coefficient of resistance in antiperovskite Mn3Ag1 xCuxN, Appl. Phys. Lett. 98 (2) (2011) 022103. [16] T. Kaneko, T. Kanomata, K. Shirakawa, J. Phys. Soc. Jpn. 56 (1987) 4047. [17] J.L. Wang, et al., J. Appl. Phys. 92 (2002) 1453.
Contents lists available at ScienceDirect
Journal of Magnetism and Magnetic Materials journal homepage: www.elsevier.com/locate/jmmm
The magnetism and electronic transport properties of Mn3Sn1 xSixC Yongchun Wen b, Cong Wang a,n, Man Nie a, Ying Sun a,b a b
Center of Condensed Matter and Materials Physics, Department of Physics, Beihang University, Beijing 100191, People's Republic of China School of Materials Engineering, YanCheng Institute of Technology, YanCheng 224051, People's Republic of China
art ic l e i nf o
a b s t r a c t
Article history: Received 6 May 2013 Received in revised form 13 April 2015 Accepted 27 April 2015 Available online 28 April 2015
The lattice, magnetic and electronic transport properties of the compounds Mn3Sn1 xSixC (0 r x r0.4) are investigated. The results have shown that Si-doping in the antiperovskite Mn3SnC induces the decrease of the nearest neighbouring Mn–Mn bond distance of Mn3Sn1 xSixC, and the magnetic structure transforms from ferrimagnetic to antiferromagnetic when x Z0.2. With the increase of Si, the Neel temperature TN rises. The TN of Mn3Sn1 xSixC(x ¼0.2, 0.3, 0.4) are 217 K, 257 K and 290 K, respectively. However, the magnetovolume effect is quenched. In Mn3SnC and Mn3Sn1 xSixC (x ¼0.2, 0.3, 0.4) compounds, there exists an anomalous increase in resistivity at a certain temperature that coincides well with their Curie temperature TC or Neel temperature TN. The temperature dependence of the resistivity of Mn3Sn1 xSixC (x ¼0, 0.2, 0.3, 0.4) exhibits semiconducting-like behavior at low temperature and metallic-like behavior at high temperature. & 2015 Published by Elsevier B.V.
Keywords: Antiperovskite structure Mn3Sn1 xSixC Electronic transport
1. Introduction Antiperovskite manganese compounds Mn3AX (A¼Sn, Ga, Zn, and Ni, etc. X ¼carbon or nitrogen), in which the Mn atoms are located on the face centered positions, the A atoms on the cubic corners, and the non-metal X atom at the body centered position in a cubic lattice, are well known for a couple of years [1]. These compounds show a wide variety of interesting physical phenomena such as superconductivity, magnetoresistivity, and a nearly zero temperature coefficient of resistivity [2–5]. In particular, the antiperovskite manganese compounds exhibit intriguing magnetic structure, and show abundant magnetic transition, abnormal transport and lattice variation [6–9]. Therefore, these compounds have attracted great attentions in recent years [10–15]. Antiperovskite structured Mn3SnC has a cubic crystal structure with space group Pm3¯ m. In spite of the simple crystal structure, Mn3SnC possesses a complicated spin arrangement of noncollinear ferrimagnetic (FI) state, consisting of an antiferromagnetic (AFM) and ferromagnetic (FM) sublattices, exiting up to the Curie temperature TC, 265 K [6]. The magnetic structure is non-collinear: the magnetic moments at MnI and MnII sites in Fig.1 have a ‘square configuration’ with μ(MnI)¼ μ(MnII)¼ 2.4 μB and a ferromagnetic component of 0.2 μB along the [001] direction on each of these sites. The magnetic moments on MnIII sites align ferromagnetically with μ(MnIII)¼ 0.65 μB along the [001] direction [6]. The results by n
Corresponding author. E-mail address: [email protected] (C. Wang).
http://dx.doi.org/10.1016/j.jmmm.2015.04.111 0304-8853/& 2015 Published by Elsevier B.V.
neutron diffraction showed that the magnetic moments of Mn atoms are much smaller than 4 μB observed in other ordered manganese alloys [8], indicating a strong itinerant characteristic of d electrons in the Mn atoms in Mn3SnC. With increasing temperature, the transition from ferrimagnetic (FI) to the paramagnetic (PM) state is accompanied by an abrupt contraction of the lattice without change of the type of the crystal structure, i.e. a negative thermal expansion (NTE) behavior occurs. Meanwhile, an abnormal change of resistivity exist in the material. In our another anti-perovskite manganese nitride Mn3Zn1 xGexN, the starting temperature point and range where the NTE appeared were increased by Ge-doping [7,10], which are beneficial to the applications of NTE materials. In order to further reveal the effects of doped elements on the lattice, magnetic and electronic transport properties and try to develop new applicable materials, Mn3Sn1 xSixC compounds are investigated in this paper.
2. Experimental details The samples Mn3Sn1 xSixC (x ¼0, 0.1, 0.2, 0.3, 0.4) were prepared using manganese, tin, silicon, and graphite powders with purity 99.95% as the starting powder materials. They were mixed in the stoichiometric proportion and pressed into pellets. The pellets were wrapped by tantalum foil, and then placed in an evacuated quartz tube. The samples were sintered in a box furnace at 800 °C for 5 days, then cooled down to room temperature. X-ray diffraction patterns at room temperature were collected
Y. Wen et al. / Journal of Magnetism and Magnetic Materials 391 (2015) 22–25
23
Fig. 3. Variation of the lattice constant of Mn3Sn1 xSixC (x ¼ 0, 0.1, 0.2, 0.3, 0.4) with increasing Si-doped content x.
Fig. 1. The antiperovskite structure and magnetic structure of Mn3SnC. The section z ¼1/2 shows the antiferromagnetic square arrangement of MnI and MnII atoms.
Fig. 4. Temperature dependence of the resistivity (rectangles) and the susceptibility (triangles) of the Mn3SnC compound. The arrow indicates the Curie temperature Tc.
3. Results and discussion
Fig. 2. X-ray diffraction patterns of the Mn3Sn1 xSixC compounds.
in a Rigaku D/MAX 2200PC diffractometer using Cu Kα radiation. Software named Powder X [9] was used for indexing and lattice constant calculation. For the measurement of coefficient of thermal expansion (CTE), variable temperature X-ray diffraction from 150 K to 325 K was used to measure the variation of lattice constant on an X’Pert PRO MPD diffractometer. Magnetic susceptibility was measured by a physical property measurement system (PPMS) from 100 K to 350 K at 50 Oe magnetic field. Electrical resistivity measurements (100–300 K) were accomplished using the standard four-probe technique.
Fig. 2 shows the XRD patterns of the Mn3Sn1 xSixC (x ¼0, 0.1, 0.2, 0.3, 0.4) samples that pure antiperovskite cubic structure was formed for these samples. All of the space groups of Mn3Sn1 xSixC are Pm3¯ m, and their lattice parameters are 3.9916 Å, 3.9850 Å, 3.9773 Å, 3.9709 Å, and 3.9655 Å for x ¼0, 0.1, 0.2, 0.3, 0.4, respectively. The lattice constant of Mn3Sn1 xSixC linearly decreases with the increase of x (seen in Fig. 3.), which indicates that Sn is really substituted by Si since the atomic radius of Si (1.32 Å) is smaller than the one of Sn (1.62 Å). The temperature dependence of the resistivity and susceptibility of Mn3SnC is shown in Fig. 4. With increasing temperature, the transition from ferrimagnetic (FI) to the paramagnetic (PM) state takes place. The susceptibility slowly decreases from 150 K to 250 K, and then rapidly drops from 250 K to 280 K. The variation of resistivity with temperature displays metallic-type at low temperatures (T o165 K), and changes into semiconducting-type in the range of 165–269 K. Evidently, the two curves indicate that with decreasing temperature, there exists an anomalous increase in resistivity at 272 K which is in good agreement with their Curie temperature 275 K (i.e., the transition temperature TPM-FI). Namely, the abnormal electronic transport behavior originates from a
24
Fig. 5. Temperature dependence Mn3Sn1 xSixC compounds at 50 Oe.
Y. Wen et al. / Journal of Magnetism and Magnetic Materials 391 (2015) 22–25
of
the
magnetic
susceptibility
of
the
transition from the PM state to the FI state. Fig. 5 presents the temperature dependence of the magnetization for Mn3Sn0.8Si0.2C, Mn3Sn0.7Si0.3C and Mn3Sn0.6Si0.4C compounds. The overall behaviors of the magnetic susceptibility for the three samples display an AFM transition, and the Neel points (TN) are 217 K, 257 K and 289 K, respectively. Namely, the Si-doping changes the magnetic phase transition. It may be that dopingSi makes the Mn–C octahedron distort, and further changes the Mn–Mn exchange integral. For Mn3SnC, the transition from ferrimagnetic (FI) to the paramagnetic (PM) state is accompanied by an abrupt contraction of the lattice without change of the type of the crystal structure [6,16], i.e. a negative thermal expansion (NTE) behavior exists. The abnormal change of the lattice constant with the coefficient of thermal expansion (CTE) αl ¼ 38 10 6 K 1 is observed at about 200–250 K (ΔT ¼50 K) for Mn3SnC. However, The NTE behavior disappears in Mn3Sn0.8Si0.2C, Mn3Sn0.7Si0.3C and Mn3Sn0.6Si0.4C. The CTEs are 9.7 10 6 K 1 (T o213 K), 20 10 6 K 1 (T4 213 K) for Mn3Sn0.8Si0.2C, 5.1 10 6 K 1 (T o255 K), 15 10 6 K 1 (T 4255 K) for Mn3Sn0.8Si0.2C and 3.6 10 6 K 1 (T o283 K), 17 10 6 K 1 (T 4283 K) for Mn3Sn0.6Si0.4C. The temperature dependence of the lattice constant for Mn3Sn1 xSixC (x ¼0, 0.1, 0.2, 0.3, 0.4) is shown in Fig. 7. A series of Mn3Sn1 xSixC remains cubic structure over a whole temperature range. There is a small discontinuous point nearly corresponding to the TN. Owing to the magnetovolume effect (MVE) [17], the spontaneous magnetization in Mn3Sn1 xSixC changes the magnetic atomic distance, and then induces the change of lattice volume, which counteracts the normal thermal expansion. According to Landau theory, the relative volume expansion ωs (ΔV/V) due to MVE is proportional to magnetoelastic coefficients C and the square of spontaneous magnetization Ms2, i.e. ωs ∝ CMs2. For most solid materials, the magnetoelastic coefficient C is very low and the ωs is quite small, and so these materials expand when heating due to the asymmetry of the closest atomic potential well. However, we speculate that the ωs of Mn3SnC is rather big, and its C is also big. With decreasing temperature, the occurrence of ωs near the Curie temperature TC makes the lattice volume enlarge, then results in negative CTE. Sidoping in Mn3SnC may decrease magnetoelastic coefficient C, the MVE gets smaller, and therefore the CTE becomes positive for Mn3Sn0.8Si0.2C and Mn3Sn0.6Si0.4C. However the thermal expansion curves of the two compounds display discontinuous points, which indicates that the MVE still exists. Fig. 8 shows the temperature dependence of the resistivity for Mn3Sn0.9Si0.1C, Mn3Sn0.8Si0.2C, Mn3Sn0.7Si0.3C and Mn3Sn0.6Si0.4C.
Fig. 6. With cubic perovskite symmetry and wave-vector k¼ [000] the group theoretical analysis permits: Γ4g (a) and Γ5g (b) two triangular antiferromagnetic atoms are drawn in the cubic unit-cell.
Y. Wen et al. / Journal of Magnetism and Magnetic Materials 391 (2015) 22–25
25
4. Conclusion
Fig. 7. Temperature dependence of the lattice constants for Mn3Sn1 xSixC.
With introducing the element Si in the antiperovskite structured Mn3SnC, the Mn–Mn distance of Mn3Sn1 xSixC decreases, the magnetic structure changes from FI into AFM when xZ 0.2. When the Si content increases, the negative thermal expansion effect gradually disappears. For Mn3SnC and Mn3Sn1 xSixC (x¼ 0.2, 0.3, 0.4) compounds, there exists an anomalous increase in resistivity at a certain temperature that is in agreement with their Curie temperature TC or Neel temperature TN. The temperature dependence of the resistivity of Mn3Sn1 xSixC (x ¼0, 0.2, 0.3, 0.4) shows semiconducting-type behavior at low temperature and metallic-type behavior at high temperature. Since the Fermi level lies just above a sharp peak of the DOS for Mn3Sn1 xSixC (x ¼0, 0.2, 0.3, 0.4), a shift of the Fermi energy surface probably due to spin polarization can result in an abrupt decrease of the DOS near the Fermi level, which could lead to a pronounced decrease of the effective number of conduction electrons. Correspondingly, the resistivity is enhanced significantly at the transition temperature (Fig. 6).
Acknowledgments This work is supported by National Natural Science Foundation of China (NSFC) (Nos. 51172012, 91122026, and 51472017). We are also grateful to the key laboratory for Ecological–environment Materials of Jiangsu Province and the Natural Science Foundation of China (No: 51402251).
References
Fig. 8. Temperature dependence of the resistivity for Mn3Sn1 xSixC.
For the three compounds, the similar variation of resistivity shows semiconductor-like behavior at low temperature and a metalliclike behavior at high temperature. With increasing temperature, there is obvious change in the transport behavior from semiconducting-type to metal-type at about 225 K, 250 K and 290 K, for Mn3Sn0.8Si0.2C, Mn3Sn0.7Si0.3C and Mn3Sn0.6Si0.4C, respectively. These transition temperatures are in agreement with their Neel temperature TN. Namely, these anomalous behaviors originate from a transition from the paramagnetic state to the antiferromagnetic state. As reported early [8], the 1st principle calculation for Mn3SnC showed that the Fermi energy level located in a sharp peak of the DOS curve. This implies that a small shift of the Fermi energy surface can result in an abrupt decrease of the DOS near the Fermi energy level, which could lead to a pronounced decrease of the effective number of conduction electrons. Correspondingly, the resistivity could be enhanced significantly at the transition temperature for Mn3SnC. However the increasing degree slows down with increasing Si-doping in Mn3Sn0.8Si0.2C, Mn3Sn0.7Si0.3C and Mn3Sn0.6Si0.4C. The Si-doping slightly changes the structure of energy band, but the basic trend of the resistivity is not changed largely.
[1] E.F. Bertaut, D. Fruchart, J.P. Bouchaud, R. Fruchart, Solid State Commun. 6 (1968) 251. [2] R. Prozorov, A. Snezhko, T. He, R.J. Cava, Phys. Rev. B 68 (2003) 180502. [3] A.F. Dong, G.C. Che, W.W. Huang, S.L. Jia, H. Chen, Z.X. Zhao, Physica C 422 (2005) 65. [4] K. Kamishima, T. Goto, H. Nakagawa, N. Miura, M. Ohashi, N. Mori, T. Sasaki, T. Kanomata, Phys. Rev. B 63 (2000) 024426. [5] E.O. Chi., S. Kim, N.H. Hur, Solid State Commun. 120 (2001) 307. [6] D. Fruchart, E.F. Bertaut, J. Phys. Soc. Jpn. 44 (1978) 781. [7] Cong Ying Sun, Yongchun Wang, Wen, Kaigui Zhu, Appl. Phys. Lett. 91 (2007) 231913. [8] K. Motizuki, H. Nagai, J. Phys. C 21 (1988) 5251. [9] K. Takenaka, H. Takagi, Zero thermal expansion in a pure-form antiperovskite manganese nitride, Appl. Phys. Lett. 94 (13) (2009) 131904. [10] Lihua Cong Wang, Qingrong Chu, Ying Yao, Meimei Sun, Lei Wu, Jun Ding, Yuanyuan Yan, Weihua Na, Guannan Tang, Qingzhen Li, Huang, Jeffrey Lynn, Tuning the range, magnitude, and sign of the thermal expansion in intermetallic Mn3(Zn, M)xN(M ¼Ag, Ge), Phys. Rev. B 85 (2012) 220103. [11] Wen Yongchun Sun Ying, Chu Lihua, Nie man, Wang Cong, Abnormal thermal expansion in anti-perovskite magnanese intride, J. Chin. Ceram. Soc. 37 (2009) 73. [12] Lei Ding, Cong Wang, Lihua Chu, Jun Yan, Yuanyuan Na, Qingzhen Huang, Xiaolong Chen, Near zero temperature coefficient of resistivity in antiperovskite Mn3Ni1 xCuxN, Appl. Phys. Lett. 99 (25) (2011) 251905. [13] Cong Ying Sun, Lihua Wang, Yongchun Chu, Man Wen, Nie, Fusheng Liu, Low temperature coefficient of resistivity induced by magnetic transition and lattice contraction in Mn3NiN compound, Scr. Mater. 62 (9) (2010) 686. [14] Cong Lihua Chu, Jun Wang, Yuanyuan Yan, Lei Na, Ying Ding, Sun, Yongchun Wen, Magnetic transition, lattice variation and electronic transport properties of Ag-doped Mn3Ni1 xAgxN antiperovskite compounds, Scr. Mater. 67 (2) (2012) 173. [15] K. Takenaka, A. Ozawa, T. Shibayama, N. Kaneko, T. Oe, C. Urano, Extremely low temperature coefficient of resistance in antiperovskite Mn3Ag1 xCuxN, Appl. Phys. Lett. 98 (2) (2011) 022103. [16] T. Kaneko, T. Kanomata, K. Shirakawa, J. Phys. Soc. Jpn. 56 (1987) 4047. [17] J.L. Wang, et al., J. Appl. Phys. 92 (2002) 1453.