Effects of light irradiation and thermal heating on interlayer coupling in Fe-Si ferromagnetic metal/semiconductor superlattices

点击翻译按钮获取中文摘要

Spin-dependent phenomena have recently received much attention. Particularly, interlayer couplings between ferromagnetic layers separated by nonmagnetic metal and insulator spacer layers have been investigated to a large extent since they can induce the spin-dependent scattering of conduction carriers and spin-dependent tunneling, which are exploited for achieving the giant magnetoresistance (GMR) and tunnel magnetoresistance (TMR) effects, respectively. At present, the switching of interlayer couplings is made by applied magnetic fields. In this study, in order to switch them by the other methods such as light irradiation, thermal heating, and current injection, semiconducting interlayers were employed. Actually ferromagnetic Fe_3Si/semiconducting FeSi_2 superlattices were prepared by sputtering and interlayer couplings were attempted to be switched by their methods. Although current in plane (CIP) films exhibited a change in the electrical resistivity for irradiation with a 1.3-μm la … More ser, which was expected to be due to a change in the interlayer coupling from antiferromagnetic (AF) to ferromagnetic (F) coupling, the change in the electrical resistivity was extremely small to be detected. Thus, we adapted current perpendicular plane (CPP) geometry for the detection. Owing to that, the magnetoresistance ratio was enhanced to be approximately 10%. This value is an order of magnitude larger than that of the CIP films. The CPP films exhibited hysteresis loops for the injection current. From the change in the hysteresis loop under magnetic field, the origin of the hysteresis loops was expected to be a change in the interlayer coupling. It was confirmed that the interlayer coupling of the CPP films was obviously changed from AF coupling at room temperature to F coupling at temperatures of lower than 100 K. The CPP films also exhibited temperature-dependent interlayer couplings : AF coupling in a direction perpendicular to the plane induced at room temperature gradually weakened with a decrease in temperature and it finally disappeared at low temperatures. Less