Oscillatory Interlayer Exchange Coupling in Amorphous CoSiB/Pt/CoSiB Structure

Abstract

Oscillatory interlayer exchange coupling is found in amorphous CoSiB(1.5 nm)/Pt(t Pt )/CoSiB(1.5 nm) structure as a function of the Pt layer thickness, t Pt , which is varied from 1.4 to 3.0 nm. We prepared the samples by using dc magnetron sputtering method, and measured anomalous Hall resistance and magnetization hysteresis loops. All the samples show out-of-plane easy axes with perpendicular magnetic anisotropy energies. Surprisingly, strong antiferromagnetic interlayer exchange coupling is found when t Pt = 2.2 ~ 2.7 nm, otherwise they are simple ferromagnets like multilayer systems of Co/Pt and Fe/Pt. The Pt layer is known as nearferromagnet, because it is easily polarized with adjacent ferromagnetic layer or by small amount of ferromagnetic impurities. The interlayer coupling via Pt has been always observed to be ferromagnetic so far. We report the antiferromagnetic interlayer exchange coupling in amorphous CoSiB/Pt/CoSiB trilayer structure, and propose its possible physical origin based on quantum well theory and negative spin polarization of Pt layer.Index Terms-Amorphous ferromagnet, interlayer exchange coupling, magnetic multilayers, perpendicular magnetic anisotropy 0018-9464 (c)

Interface mixing and its impact on exchange coupling in exchange biased systems

“…Let us consider the presence of IEC between the two FM layers, viz. Ni 80 Fe 20 and Co. Possible evidence of its presence is the variation of saturation magnetization with interlayer thickness [54][55][56]. Since CoO is an antiferromagnet that has no net magnetization in this system and the thicknesses of both FM layers are same for all three trilayers, a variation in FM volume normalized (excluding the intermixed ferrite region in the volume calculation) saturation magnetisation (M FM nor ) is not expected if there is no IEC.…”