Department of Physics, Thin Films and Physics of Nanostructures, Bielefeld University, Bielefeld, Germany.
J Phys Condens Matter. 2011 Mar 23;23(11):116005. doi: 10.1088/0953-8984/23/11/116005. Epub 2011 Mar 3.
The generalized Heusler compounds Mn(2)CoZ (Z = Al, Ga, In, Si, Ge, Sn, Sb) with the Hg(2)CuTi structure are of great interest due to their half-metallic ferrimagnetism. The complex magnetic interactions between the constituents are studied by means of first principles calculations of the Heisenberg exchange coupling parameters, and Curie temperatures are calculated from those. Due to the direct Mn-Mn exchange interaction in Mn(2)CoZ, the Curie temperature decreases, although the total moment increases when the valence electron number Z is increased. The exchange interactions are dominated by a strong direct exchange between Co and its nearest neighbor Mn on the B site, which is nearly constant. The coupling between the nearest neighbor Mn atoms scales with the magnetic moment of the Mn atom on the C site. Calculations with different lattice parameters suggest a negative pressure dependence of the Curie temperature, which follows from the decreasing magnetic moments. Curie temperatures of more than 800 K are predicted for Mn(2)CoAl (890 K), Mn(2)CoGa (886 K), and Mn(2)CoIn (845 K).
Hg2CuTi 结构的 Mn2CoZ（Z=Al、Ga、In、Si、Ge、Sn、Sb）广义 Heusler 化合物由于其具有半金属铁磁性而备受关注。通过 Heisenberg 交换耦合参数的第一性原理计算研究了成分之间复杂的磁相互作用，并从这些参数计算了居里温度。由于 Mn2CoZ 中存在直接的 Mn-Mn 交换相互作用，尽管价电子数 Z 增加时总磁矩增加，但居里温度却降低了。交换相互作用主要由 B 位上 Co 和其最近邻 Mn 之间的强直接交换主导，该相互作用几乎是恒定的。最近邻 Mn 原子之间的耦合与 C 位上 Mn 原子的磁矩成正比。不同晶格参数的计算表明，居里温度随压力呈负相关，这是由于磁矩减小所致。对于 Mn2CoAl（890K）、Mn2CoGa（886K）和 Mn2CoIn（845K），预测其居里温度超过 800K。
