Spin-canted magnetism and decoupling of charge and spin ordering in NdNiO3

We report detailed magnetization measurements on the perovskite oxide NdNiO3. This system has a first order metal-insulator (M-I) transition at about 200 K which is associated with charge ordering. There is also a concurrent paramagnetic to antiferromagnetic spin ordering transition in the system. We show that the antiferromagnetic state of the nickel sublattice is spin canted. We also show that the concurrency of the charge ordering and spin ordering transitions is seen only while warming up the system from low temperature. The transitions are not concurrent while cooling the system through the M-I transition temperature. This is explained based on the fact that the charge ordering transition is first order while the spin ordering transition is continuous. In the magnetically ordered state the system exhibits divergence between zero field cooled and field cooled magnetizations, as well as history-dependent magnetization and aging. Our analysis rules out the possibility of spin glass or superparamagnetism and suggests that the irreversibility arises from magnetocrystalline anisotropy and domain wall pinning.