Effect of frozen spin on the magnetocaloric property of La0.7Ca0.3CoO3 polycrystalline and single crystal samples

► ΔSM shows a very large inverse irreversibility value for the ZFC process. ► The −ΔSM shows a normal positive value for the FC process. ► Cluster-spin-glass (CSG) states exist in polycrystalline sample. ► Much simpler magnetic phase regime in single crystal sample. ► CSG induced a magnetic field memory effect and an exchange-bias-like effect.