Giant magnetoresistance effect and magnetic anisotropy in Co 9Fe⧸Cu⧸Co 9Fe trilayers on MgO(110) substrates

Abstract

Magnetoresistive properties were investigated for Co 9Fe/Cu/Co 9Fe trilayers with a 21 Å Cu layer thickness and different Co 9Fe layer thickness which were prepared on MgO(110) substrates using ion beam sputter deposition. The influence of a 50 Å Fe buffer was also investigated. The films grew with epitaxial relations of MgO(110) [110] ‖ Co 9Fe(110)[110] and MgO(110)[110] ‖ bccFe(211)[111] ‖ Co 9Fe(110)[110] without and with a Fe buffer layer, respectively. In-plane uniaxial magnetic anisotropy ( K u) in addition to cubic anisotropy ( K 1) was induced, of which the easy axis was along MgO[001] and MgO[110] without and with a 50 Å Fe buffer layer, respectively. The magnetoresistance (MR) ratio decreased monotonically with increasing Co 9Fe layer thickness in the investigated thickness range, 25–70 Å. The maximum value obtained was 11.5% at room temperature. With increasing field the MR saturated with a gentle slope after a steep drop at a small field without a Fe buffer layer, but rapidly saturated at a small field with a Fe buffer. These behaviours can be understood by magnetization processes taking into account both K u and K 1.