Exploring the possible origin of spin reorientation transition in NdCrO$_3$.

Spin reorientation transitions and other related magnetic phenomena, which owe their origin to the complex interplay between multiple magnetic sublattices, have long attracted scientific attention both from the perspective of fundamental curiosity and technological applications. In this study, combining first principles calculations together with finite temperature Monte Carlo simulations, we explore the possible origins of reorientation transition of Cr spins in NdCrO$_3$. We construct a NdCrO$_3$ specific magnetic model, consisting of symmetric superexchange interactions between magnetic ions, as well as their magnetic anisotropy. We show that the observed spin reorientation in NdCrO$_3$, arises out of a delicate balance between Nd$-$Cr magnetic exchange interactions, single ion anisotropy of Nd spins, and single ion anisotropy of Cr spins. Moreover, though our model does not take into consideration the effect of anti-symmetric and anisotropic-symmetric magnetic exchanges, the qualitative as well as quantitative agreement of the theoretically derived and the experimentally observed spin-reorientation transition in NdCrO$_3$, confirms the merit of our proposed microscopic model. Our results also propose a hitherto unobserved collective magnetic ordering in Nd sublattice, which is challenging to detect as it is an extreme low temperature phenomena, therefore calls for further investigations.