Abstract
The exchange bias effect at ferromagnetism (FM)/antiferromagnetism(AFM) interface is a key on developing spintronic technologies with new functionality. It is well known that chemically ordered FeRh alloys with the CsCl structure show the fascinating first order magnetic phase transition from the antiferromagnetic to ferromagnetic states at around 370 K upon heating from room temperature, accompanied by an isotropic volume expansion of about 1%, a large reduction in the resistivity and a large change in entropy. FeRh thin films were prepared by magnetron sputtering on MgO(001) substrates and annealed in the temperature range of 700-900 ℃. The structure was characterized by X-ray diffraction and it showed an epitaxial FeRh thin film on MgO(001) substrates and on BaTiO3 buffered SrTiO3(001) substrates. In this paper, the structures and magnetic properties of phase transition are analyzed by using X-ray diffraction, X-ray reflectivity, scanning electron microscope and physical property measurement system. In particular, here we probe the AFM/FM of FeRh interface magnetization, and identify a new exchange bias phenomena. This is the first homogenous system with exchange bias without having a hetergenous interface of FM/AFM layer. One of the possible reason is due to the strain at interface which induced an AFM FeRh layer under the FM FeRh layer. The other possibility could be due to the interdiffusion of atoms from neighboring layer into FeRh at higher temperature resulting in change of FM/AFM phase transition temperature, so that AFM is formed in the heavy doped FeRh layer under the FM FeRh layer.