Magnetic-Field-Induced Insulator–Metal Transition in (Pr1−yYy)0.7Ca0.3CoO3 at Ultrahigh Magnetic Fields

The (Pr1−yYy)0.7Ca0.3CoO3 (y ≥ 0.0625) compounds show a first-order metal–insulator (MI) transition and simultaneous spin-state (SS) transition upon a change in the temperature. We have measured the electrical resistivity of the samples with y = 0.075 (the transition temperature, TMI = 64 K) and 0.10 (TMI = 93 K) in ultrahigh magnetic fields of up to 120 T using a contactless radio-frequency transmission technique. We observed a magnetic-field-induced insulator–metal (IM) transition with large hysteresis below TMI and obtained the temperature–magnetic field phase diagrams. A possible mechanism of the field-induced IM and SS transitions is discussed.