Spin Switching and Magnetization Reversal in Single-Crystal NdFeO$_3$

We report results of our recent study of single-crystal NdFeO$_3$ that features a strong interaction between 3d and 4f electrons, which generates \textit{two distinct magnetic states} ordered at 17 K and 170 K. This study reveals novel magnetic behavior that is highly sensitive to the orientation and history of magnetic field and is characterized by the following: \textbf{(1)} sharply contrasting magnetization, M(T), along the \textbf{\textit{a}} and \textbf{\textit{c}}-axis; \textbf{(2)} an abrupt spin-switching along the \textbf{\textit{a}}-axis via a first-order transition below 17 K when the system is \textit{zero-field-cooled}; and \textbf{(3)} a progressive magnetization reversal when the system is \textit{field-cooled}. Such behavior suggests an exotic ground state driven by an extraordinary coupling between spin, orbit and lattice degrees of freedom.