A 90° ferromagnetic layer coupling in FM/AFM/FM structures

Abstract

The magnetic anisotropy in the samples of Ta (5 nm)/NiFe (8 nm)/FeMn ( t AF)/NiFe (8 nm)/Ta (5 nm) with t AF=0–30 nm were studied by using a vibrating sample magnetometer (VSM) and ferromagnetic resonance (FMR). Unidirectional anisotropy field ( H B) and uniaxial anisotropy field ( H A) having strength comparable with literatures and easy axes in the direction of the field during deposition were observed in the bottom Py layers, a smaller H B with easy axis parallel to the deposition field in the top Py layer was also observed. An interesting finding was that an additional uniaxial anisotropy in the top Py layer appeared with the easy axis perpendicular to the direction of field during deposition. A possible explanation for the 90° coupling between the bottom and top Py layers through the intervening antiferromagnetic FeMn film is considered to be interface roughness.