Magnetic force microscope study of antiferromagnet–ferromagnet exchange coupled films

Magnetic microstructure in micron and submicron size elements made of bilayer antiferromagnet–ferromagnet (AFM/FM) (AFM: NiMn, PtMn, and IrMn; FM: NiFe and CoFe) exchange coupled polycrystalline films have been studied using a magnetic force microscope. AFM/FM elements with various thickness of FM layer (50–500 A) have been examined and compared with nonexchange biased FM elements of the same size, shape, and thickness. Micromagnetic structures observed in AFM/FM elements with thick (>200 A) FM layer indicated that, in addition to unidirectional anisotropy, the AFM layer induces uniaxial anisotropy in a FM layer. Bilayers with a NiMn or PtMn AFM layer exhibited higher induced uniaxial anisotropy than ones with IrMn. In the elements with a thin (