纯γ-Mn的电子、基态属性和磁有序结构

ELECTRONIC STRUCTURE, GROUND PROPERTIES AND MAGNETIC ORDERING FOR PURE γ-Mn

采用第一原理方法,基于ultrasoft赝势、密度函数理论,从原子层面对纯γ-Mn的顺磁、铁磁和反铁磁性状态下的电子、基态属性、相稳定和磁有序结构进行了研究.通过自旋极化分析讨论了纯γ-Mn这3种磁性状态的结构稳定性,发现在基态时,反铁磁性状态的γ-Mn结构最稳定,且Mn原子处于高自旋状态,其理论磁通量为2.41μB/atom,这与实验结果吻合通过局部状态密度（DOS）,分析了它们的键和磁有序特性,发现主要是位于Fermi态附近的3d轨道电子对磁性起决定性的作用,其向上自旋和向下自旋的主峰分别处于Fermi能下面的键区和Fermi能上面的反键区.通过比较这3种磁性状态可知,反铁磁的γ-Mn存在显著的磁体积效果.

The atomic structure, electronic, and magnetic ordering properties, phase stability of pure γ-Mn have been investigated by the first principle density-functional calculations based on ultrasoft pseudopotentials for paramagnetic, ferromagnetic, and antiferromagnetic states, respectively. It has been found that the antiferromagnetic structure at ground state is the most stable by the spin-polarized calculation and the local theoretical magnetic moment is 2.43 μB/atom for pure γ-Mn in a high-spin state in excellent agreement with experimental results. The bonding nature and magnetic ordering of these structures have also been analyzed via the density of states (DOS) histogram. It is found that the origin of antiferromagnetic properties existing in pure γ-Mn is mainly determined by the electrons of 3d orbits around Fermi energy, and the main peaks for spin-up and spin-down site in the bonding and anti-bonding regions. Detailed comparisons of such three structures revealed that the antiferromagnetic state for pure γ-Mn has the prominent magnetovolume effect.