Bilinear and Biquadratic Exchange Coupling in BCC Fe/Cu/Fe Trilayers. Exchange Coupling in Fe Whisker/Cr/Fe(001) Structures

Abstract

Surface Magneto-Optical Effect (SMOKE) studies of the exchange coupling in bcc Fe/Cu/Fe(001) structures and Brillouin Light Scattering (BLS) results on Fe(OOl) whisker/Cr/Fe(001) structures are presented. It is shown that the interfaces in bcc Fe/Cu/Fe(001) trilayers can be significantly improved by choosing an appropriate growth procedure. The exchange coupling in bcc Fe/Cu/Fe trilayers was studied as a function of the interlayer thickness. The interpretation of magnetization loops for Fe/Cu/Fe trilayers requires the simultaneous presence of bilinear and biquadratic exchange coupling between the magnetic layers. Computer calculations were used to determine the strength of the bilinear and biquadratic exchange couplings. It is shown that the strength of the biquadratic exchange coupling increases with increasing terrace width. The measured values of the bilinear and biquadratic exchange coupling were compared with a model recently proposed by Slonczewski, which treats the exchange coupling in trilayers with imperfect interfaces. Slonczewski’s model was used to deconvolute the data to obtain the intrinsic behavior of the bilinear exchange coupling in bcc Fe/Cu/Fe(001) trilayers. It is shown that the exchange coupling unobscured by interface roughness exhibits a strong short wavelength oscillatory behavior which is in agreement with recent first principles band calculations.