We report an experimental and computational study of single-crystal NdFeO3, which features two inequivalent magnetic sublattices, namely, Fe and Nd sublattices that are coupled in an antiparallel fashion. This paper reveals that a strong interaction between 3d and 4f electrons of the two sublattices along with a spin-lattice coupling drives an extremely interesting magnetic state that is highly sensitive to the orientation and history of weak magnetic field. The following phenomena are particularly remarkable: (1) sharply contrasting magnetization M(T) along the a and c axes; (2) a first-order spin switching along the a axis below 29 K when the system is zero-field-cooled; and (3) a progressive magnetization reversal when the system is field-cooled. The intriguing magnetic behavior is captured in our first-principles density functional theory calculations
