Magnetism, electronic structure and optical properties of TbNiGe2

Abstract

TbNiGe2 compound crystallizes in the CeNiSi2 type orthorhombic crystal structure and shows antiferromagnetic ordering below 39 K. Magnetization isotherms show linear dependence for field up to 50 kOe. It shows inverse magnetocaloric effect, which is attributed to antiferromagnetic interactions between the moments. The resistivity data was fitted in high and low temperature regimes. The low temperature fit confirms the antiferromagnetic ordering, while the high temperature data follow Bloch-Grüneisen-Mott relation. Ab initio LSDA + U calculations show no spin polarization from Ni 3d electronic states and reproduce the antiferromagnetic long-range ordering of the Tb magnetic moments and their values in good agreement with the previous neutron diffraction data. Optical conductivity data supports the electronic structure calculations and show that it is mostly provided by the transitions involving Ni 3d and Tb 4f electronic states.