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

与自旋相关的现象最近受到了广泛的关注。特别是，被非磁性金属隔开的铁磁层和绝缘体隔离层之间的层间耦合已经得到了很大程度的研究，因为它们可以引起导电载流子的自旋相关散射和自旋相关的隧道效应，这两种效应分别被用来实现巨磁电阻(GMR)和隧道磁阻(TMR)效应。目前，层间耦合的转换是通过外加磁场来实现的。在本研究中，为了通过光照射、热加热和电流注入等其他方法来实现它们的转换，采用了半导体中间层。用溅射法制备了铁磁性Fe3Si/半导体FeSi2超晶格，并尝试用其方法实现层间耦合的转换。尽管平面电流(CIP)薄膜在1.3-μm la…辐照下的电阻率发生了变化更严重的是，由于层间耦合从反铁磁(AF)耦合转变为铁磁(F)耦合，电阻率的变化非常小，无法检测到。因此，我们采用了当前的垂直平面(CPP)几何结构来进行检测。因此，磁电阻率提高到约10%。该值比CIP膜的值大一个数量级。CPP薄膜在注入电流的作用下表现出磁滞回线。从磁滞回线在磁场作用下的变化可知，磁滞回线的起因可能是层间耦合的变化。结果表明，CPP薄膜的层间耦合在100K以下发生了明显的变化，从室温下的AF耦合转变为低温下的F耦合。CPP薄膜还表现出依赖温度的层间耦合：在室温下，垂直于平面方向的AF耦合随着温度的降低而逐渐减弱，在低温下逐渐消失。较少

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