  We report detailed magnetization measurements on the perovskite oxide
NdNiO$_3$. 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
ZFC-FC irreversibilities, as well as history-dependent magnetization and aging.
Our analysis rules out the possibility of spin-glass or superparamagnetism and
suggests that the irreversibilities originate from magnetocrystalline
anisotropy and domain wall pinning.
