Open AccessA band Jahn-Teller effect in the martensitic phase transition of the Heusler alloy Mn2NiGe
Author(s) -
Luo Li-Jin,
Zhong Chong-Gui,
Zhengchao Dong,
Fang Jing-Huai,
Zhou Peng-Xia,
Xuefan Jiang
Publication year - 2012
Publication title -
wuli xuebao
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.199
H-Index - 47
ISSN - 1000-3290
DOI - 10.7498/aps.61.207503
Subject(s) - condensed matter physics , pseudogap , materials science , jahn–teller effect , octahedron , martensite , phase transition , magnetic moment , alloy , ion , magnetic shape memory alloy , crystal structure , magnetic anisotropy , physics , crystallography , magnetic field , chemistry , magnetization , superconductivity , microstructure , cuprate , quantum mechanics , metallurgy , composite material
The changes of crystal structure, magnetic structure, electronic structure in the martensitic phase transition for magnetic shape memory alloy Mn2NiGe are calculated by first-principles method. The results show that in the martensitic phase transition for Mn2NiGe, there is produced a Jahn-Teller distortion, in which the c-axis becomes longer but a-axis and b-axis turn shorter, forming an elongated octahedral geometry. There is a significant change in magnetic moment for Mn ion in the centre of octahedron, but a little change happens to the Ni and Ge ions that are regarded as a ligand. The energy levels of eg and t2g are split by redistributing the density of states for d electrons and so opening a pseudogap near the fermi energy due to lattice distortion.