Magnetic ordering in intermetallic La_(1-x)Tb_xMn_2Si_2 compounds

摘要

The magnetic structures and magnetic phase transitions in intermetallic layeredLa1-xTbxMn2Si2compounds (the ThCr2Si2-type structure) are investigated using the first-principles method and XPS measurements. The experimentally observed transition from ferromagnetic (FM) to antiferromagnetic (AFM) ordering of Mn sublattice with increase of terbium concentration is successfully reproduced in calculations for collinear magnetic moments model. TheFM→AFMchange of interplane magnetic ordering at smallxis irrelevant to the number off-electrons of the rare-earth ion. In contrast it was shown to be related to the Mn-Mn in-plane distance. Calculated Tb critical concentration for this transitionx≈0.14corresponds to the Mn-Mn in-plane distance 0.289 nm, very close to the experimentally observed transition distance 0.287 nm. The crystal cell compression due to substitution increases an overlap betweenMn dxz,yzand the rare-earth iondorbitals. Resulting hybridized states manifest themselves as an additional peak in the density of states. We suggest that a corresponding interlayer Mn-R-Mn superexchange interaction stabilizes AFM magnetic ordering in these compounds with Tb doping levelx>0.2. The results of DFT calculations are in agreement with X-ray photoemission spectra forLa1-xTbxMn2Si2.