Magnetostructural behavior in the non-centrosymmetric compound Nd₇Pd₃

A systematic study of the physical properties and microscopic magnetism of Nd₇Pd₃ compound, which in the paramagnetic state crystallizes in the non-centrosymmetric hexagonal Th₇Fe₃-type structure (hP20-P6₃ mc; with a  =  10.1367(1) Å and c  =  6.3847(1) Å at 300 K), confirms multiple magnetic ordering transitions that occur upon cooling. Antiferromagnetic transition is observed at T _N  =  37 K, which is followed by ferromagnetic transformation at T _C  =  33 K. The first-order magnetic transition at T _C is magnetoelastic: it involves a change of crystal symmetry from P6₃ mc to Cmc2₁ and leads to anisotropic changes of the unit cell parameters. While the antiferromagnetic structure is symmetry allowed in P6₃ mc, the ferromagnetic structure with magnetic moments along the a-direction of the original hexagonal unit cell induces the first order transition to Cmc2₁. Density functional theory calculations confirm the experimentally observed ground state with the a-axis as the easy magnetization direction.