Abstract
We propose the mechanism of interlayer exchange coupling in $\mathrm{Fe}∕\mathrm{Si}$ structures, based on three principal ideas: (i) Contact induced ferromagnetic phase of body-centered-cubic iron silicide and spin-polarized interfacial states are formed at the $\mathrm{Fe}∕\mathrm{Si}$ boundaries; (ii) exchange coupling between Fe layers is effectuated by means of the superexchange of spin-polarized interfacial states through the nonmagnetic semiconductor spacer; (iii) the complex character of the dependence of interlayer exchange coupling on the spacer thickness and composition is due to the competition between antiferromagnetic and ferromagnetic components of superexchange. We calculate the bilinear and biquadratic components of an exchange coupling energy in the framework of a simple two-band scheme of electron spectrum inside the spacer at zero temperature. Our model qualitatively explains existing experimental results.
Highlights
During the last years the silicon based magnetic nanostructuressandwiches, multilayers, digital, and amorphous alloysbecame a special topic of experimental and theoretical researches, due to their possible applications to spintronics.1 A number of works has been done in order to understand magnetic and transport properties of Fe/ Si layered structures
We propose the mechanism of interlayer exchange coupling in Fe/ Si structures, based on three principal ideas: ͑i Contact induced ferromagnetic phase of body-centered-cubic iron silicide and spin-polarized interfacial states are formed at the Fe/ Si boundaries; ͑iiexchange coupling between Fe layers is effectuated by means of the superexchange of spin-polarized interfacial states through the nonmagnetic semiconductor spacer; ͑iiithe complex character of the dependence of interlayer exchange coupling on the spacer thickness and composition is due to the competition between antiferromagnetic and ferromagnetic components of superexchange
In this work we have proposed the superexchange mechanism of interlayer exchange couplingIECin Fe/ Si structures, based on the following three principal ideas
Summary
During the last years the silicon based magnetic nanostructuressandwiches, multilayers, digital, and amorphous alloysbecame a special topic of experimental and theoretical researches, due to their possible applications to spintronics. A number of works has been done in order to understand magnetic and transport properties of Fe/ Si layered structures. In a more complex electron-optic model the IEC is expressed in terms of spin-depended asymmetric reflection of quasiparticles at the insulatorferromagnetic interface Both these models predict the AFM character and exponential decay of J1͑L, as the spacer thickness L increases. The bcc modification c-FeSi appears to be stable in a form of a thin intermediate layer sandwiched by the bcc Fe layer, due to the good compatibility of the lattice parameters.20 Both the occupation and spin polarization of electron states in such a layer significantly differ from those in the bulk c-FeSi. Our principal assumption is that the spindepended interfacial potential induces the strong charge and spin redistribution at the scale of few interlayer distances. We use in the following only traditional symbol Fe/ Si for the interface
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