New magnetic phase in the nickelate perovskite TlNiO₃

The RNiO₃ perovskites are known to order antiferromagnetically below a material-dependent Néel temperature TN. We report experimental evidence indicating the existence of a second magnetically ordered phase in TlNiO₃ above T_N = 104K, obtained using nuclear magnetic resonance and muon spin rotation spectroscopy. The new phase, which persists up to a temperature T_N^* = 202K, is suppressed by the application of an external magnetic field of approximately 1T. It is not yet known if such a phase also exists in other perovskite nickelates.