Biquadratic Coupling Contributions to the Magnetoresistive Curves in Fe/FeSi/Fe Sandwiches with Semiconductor like FeSi and Metallic bcc FeSi Spacers

Magnetoresistance was investigated in Fe/FeSi/Fe sandwiches with metallic bcc- and semiconductor like FeSi spacers prepared by an ultrahigh-vacuum magnetron sputtering system, enhanced with inductively coupled RF plasma. In the easy axis direction, MR curves at 298 K have a dip around the zero magnetic field for both Fe/FeSi/Fe sandwiches with semiconductor like FeSi and bcc metallic FeSi spacers. On the other hand, MR curves at 10 K exhibit a dip and no anomaly around the zero magnetic field for the Fe/bcc metallic FeSi/Fe and Fe/semiconductor like FeSi/Fe sandwiches, respectively. When the contribution of biquadratic coupling to interlayer exchange coupling is considered, these MR behaviors are well explained. These results support the interlayer exchange coupling model attributed to the biquadratic exchange coupling which outweighs the colinear term at a low temperature in Fe/FeSi multilayers.