Giant Magneto-Optical Kerr Effects in Ferromagnetic Perovskite BiNiO3 with Half-Metallic State

We theoretically show that the giant magneto-optical Kerr effects are induced by the electronic structure of half-metallic ferromagnetism in the perovskite BiNiO3 with the orthorhombic structure by first-principles calculation. A Kerr rotation is up to 1.28° at 1.87 eV, which is comparative to the recognized maximum polar Kerr rotation of 1.35° at 1.75 eV in the Heusler compound PtMnSb. The strong p−d exchange interaction causes the half-metallic ferromagnetism, i.e., the majority-spin electrons are semiconducting and the minority-spin electrons are metallic, which finally leads to the large Kerr rotation in the half-metallic ferromagnetic perovskite BiNiO3.