Interlayer Exchange Coupling in Full Heusler $\hbox {Co}_{2}\hbox {FeSi/Cr/Co}_{2}\hbox {FeSi}$ Epitaxial Trilayer Structures

Interlayer exchange coupling was investigated in Co₂FeSi(20 nm)/Cr(t_Cr = 0.6 to 3 nm)/Co₂FeSi(7 nm) epitaxial trilayer structures by M - H loop measurement and using a numerical simulation method. The epitaxial growth and the presence of partial B2 ordering in Co₂FeSi films were confirmed from the XRD patterns. The bilinear coupling parameter J₁ and 90° coupling parameter J₂ were determined from the numerical simulation of M - H loops for trilayers. The absence of 180° coupling and the presence of dominating 90° coupling were observed from the comparison between the numerical simulations and measured M - H loops within a wide range of spacer thickness. The strength of the 90° coupling was found to vary with the spacer thickness and only a peak of J₂ was observed at t_Cr = 1.2 nm.