Impacts of nanostructuring and magnetic ordering of Nd3+ on the magnetic and magnetocaloric response in NdMnO3

Magnetocaloric properties of NdMnO3 were investigated in its bulk polycrystalline and nanocrystalline forms. The nanocrystalline sample (average particle size similar to 40 nm) exhibits a maximum in the temperature dependence of magnetic entropy change [-Delta S-M(T)] at similar to 70 K due to the paramagnetic to ferromagnetic transition, which is absent in case of its bulk counterpart. The absence of peak in -Delta S-M(T) in the bulk sample is attributed to the co-existence of antiferromagnetic and ferromagnetic phases. A canted magnetic state (CMS) is stabilized at low temperature for both the samples due to the ordering of Nd3+ giving rise to a peak in -Delta S-M(T) at similar to 15 K. Interestingly -Delta S-M(T) for these two samples show a universal behavior near their transitions at low temperature although their temperature dependence of magnetization is markedly different around those transitions. A detailed analysis of magnetocaloric data conclusively establishes the existence of a canted magnetic state, which is not obvious from magnetometry, demonstrating the usefulness of this method for probing phase coexistence and multiple magnetic states in complex oxide systems. (C) 2015 Elsevier B.V. All rights reserved