Nd-ordering-driven Mn spin reorientation and magnetization reversal in the magnetostructurally coupled compound NdMnO3

A detailed neutron diffraction study on NdMnO3 infers that the low temperature transition at 15 K is due to the ordering of Nd sublattice moment with a (0,-F-y, 0) type spin arrangement. Interestingly, the ordering of the Nd sublattice drives a reorientation (by 180 degrees.) of the net ferromagnetic moment of the Mn sublattice along the b axis. Such a Mn spin reorientation from (A(x), F-y, 0) (with an antiferromagnetic ordering temperature of 73 K) to (Ax,-Fy, 0) at 15 K, explains the magnetization reversal phenomenon present in this perovskite compound at 15 K. Moreover at 15 K, significant crystallographic structural distortions in terms of temperature variations of lattice parameters and bond angles are found. A sign change in the temperature variation of magnetic entropy is also found at 15 K. The present study signifies the role of rare-earth (Nd) moment ordering in tuning various physical properties, such as magnetocaloric andmagnetoelastic of the larger size (> 0.912 angstrom) R ion based RMnO3 compounds.