Extending the metal to insulator transitions of rare-earth nickelates towards low temperature ranges

Although the d-band correlated rare-earth nickelates (ReNiO3) exhibit broadly adjustable metal to insulator transitions (MIT) that enables emerging correlated electronic applications, it is yet difficult to regulate their associated critical temperature (T-MIT) below 100 K. Herein, we extend the lower limit in T-MIT of ReNiO3 down to 83 K while maintaining an abrupt switch in resistivity via partial La-substitution of PrNiO3. The near edge X-ray fine structure analysis and density function theory calculations indicate the strengthening in the metallic orbital configuration and reduction in the ground state band gap via La-substitution of Re in NdNiO3 and PrNiO3. In contrast, analogous Ce substitution cannot reduce the T-MIT of ReNiO3 owing to its valance variability toward +4, while La partial substitution of ReNiO3 with middle or heavy rare-earth (e.g., Sm) easily disturb the co-occupation of the Re-site by the two rare-earths as one dispersive phase.