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-P63mc; with a = 10.1367(1) A and c = 6.3847(1) A at 300 K), confirms multiple magnetic ordering transitions that occur upon cooling. Antiferromagnetic transition is observed at TN = 37 K, which is followed by ferromagnetic transformation at TC = 33 K. The first-order magnetic transition at TC is magnetoelastic: It involves a change of crystal symmetry from P63mc to Cmc21 and leads to anisotropic changes of the unit cell parameters. While the antiferromagnetic structure is symmetry allowed in P63mc, 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.