内容摘要:

本项工作系统地研究了Mn_3+xSn_1−xC(0≤x≤0.4)和Mn₃Zn_ySn_1−yC (0≤y≤0.9)的磁性和磁输运性质。三元系化合物Mn₃MC(M=Al，Ga，Zn，In和Sn)是钙钛矿型立方晶体结构。由于费米面发生改变，使得传导电子突然减少，引起Mn_3+xSn_1−xC的电阻率在T_C附近突然增加。同时伴随一个由顺磁态至铁磁或亚铁磁的磁相变。在Mn_3.2Sn_0.8C中发现其电阻率随温度的降低单调减小。用Sn部分替代Zn后，Mn₃Zn_0.4Sn_0.6C在170 K，Mn₃Zn_0.5Sn_0.5C在142 K引起铁磁或亚铁磁态向反铁磁态的转变，从而对输运性质影响较大。伴随金属磁性转变还出现了一个明显的磁电阻变化。其原因是金属磁性转变之后超布里渊区能隙的形成受到抑制，费米面重构导致的。

Temperature dependence of the resistivities of (a) Mn₃Zn_0.5Sn_0.5C and (b) Mn₃Zn_0.4Sn_0.6C compound at zero field (the solid symbols) and at a magnetic field of 5 T (the open triangle symbols) and 12 T (the open circle symbols). (c)and (d) represent the temperature dependence of the MR ratio Δρ/ρ=[(ρ_H−ρ₀)/ρ₀] of the Mn₃Zn_0.5Sn_0.5C and Mn₃Zn_0.4Sn_0.6C compounds at a field of 5 T (the open triangle symbols) and 12 T (the open circle symbols), respectively.