Magnetoresistance and magnetic properties of Fe/Cu/Fe/GaAs(100)

A procedure for growth of smooth As free Fe surfaces on (4X6)-GaAs(100) is presented. Ferromagnetic resonance (FMR) revealed that the Fe films have anisotropies equal to bulk Fe, modified only by interface anisotropies. The Fe films served as templates for the growth of epitaxial Fe/Cu/Fe trilayers which were subsequently characterized by FMR, magneto-optical Kerr effect, and magnetoresistance. At room temperature, films coupled through a 13.2-ML Cu spacer exhibited 2.0% giant magnetoresistance and 0.3% anisotropic magnetoresistance. The results showed that the interlayer exchange coupling for a 13.2-ML Cu spacer could not be described by bilinear and biquadratic contributions alone. A different coupling, which varied as cosine cubed of the angle between the magnetizations of the Fe films, was required to explain the data (bicubic exchange coupling).