Magnetic properties of NdMn 1−x Fe x O 3+δ (0≤ x ≤0.3) system

We have studied the effect of Fe for Mn substitution on magnetic properties of NdMn 1− x Fe x O 3+ δ compounds. Our heat capacity, AC susceptibility and magnetization measurements revealed that the transition from paramagnetic to magnetically ordered state of the Mn sublattice decreases linearly from T N =74.9 K to T N =49 K with doping up to x =0.25. The ordering temperature T 1 of Nd sublattice varies in a non-monotonous way in the temperature range 11–16 K. For x =0.3, the ordering of the Mn/Fe sublattice is residual, while the magnetism in Nd sublattice seems to be intact. The broad maximum in heat capacity C ( T ) at about 10 K was ascribed by 2-level Schottky contribution ( Δ =21(1) K) for x =0, but this description failed for Fe-doped samples. An upturn of C ( T ) at temperatures below 0.5 K was observed on NdMnO 3 and can be accounted to nuclear contribution. A more detailed study of AC susceptibility performed on samples with x =0.1 and 0.2 revealed a shift of both peaks to higher temperature with increasing frequency. The compensation temperature and a large negative field-cooled magnetization was observed for concentrations x =0.2 and x =0.25.