A new magnetic phase in the nickelate perovskite TlNiO${}_3$

The RNiO${}_3$ perovskites are known to order antiferromagnetically below a material-dependent N'eel temperature $T_{\text{N}}$. We report experimental evidence indicating the existence of a second magnetically-ordered phase in TlNiO${}_3$ above $T_{\text{N}}=104$ K, obtained using nuclear magnetic resonance and muon spin rotation spectroscopy. The new phase, which persists up to a temperature $T_{\text{N}}^{\ast }=202$ K, is suppressed by the application of an external magnetic field of approximately 1 T. It is not yet known if such a phase also exists in other perovskite nickelates.