High field magnetism of Sr _0.78Y _0.22CoO _3-δ under high pressure

We performed high field magnetization measurements up to 50 T on polycrystalline samples of Sr _0.78Y _0.22CoO _3-δ at 4.2 K under high pressures up to 0.48 GPa. The magnetization at 0.21 GPa or 0.48 GPa increases with field and shows an anomaly around 30 T which is ascribed to be a field-induced spin-state transition, while the magnetization at ambient pressure shows no such anomaly and increases gradually at high fields. This peculiar magnetic behavior of this compound under pressure is attributed to small bulk modulus and susceptible spin state of Co ³⁺ ions.