Xenon-ion induced magnetic and structural modifications of ferromagnetic alloys

Thin polycrystalline films of permalloy (Ni79Fe21) and permendur (Co50Fe50) have been irradiated with Xe-ions to fluences of 10(14)-10(16) ions/cm(2). Ion-induced structural and magnetic modifications have been measured by grazing angle X-ray diffraction, Rutherford backscattering and magneto-optical Kerr effect. In the case of permendur, the Xe-ion implantation first reduced the coercivity, because of stress relaxation, while higher ion fluences increased the coercivity due to pinning centers generated in the film. The ion irradiation aligned the in-plane easy axis of the magnetization along the direction of the external magnetic field during implantation. Phase shifts obtained from magnetic force microscopy confirmed these modifications. The effects of Xe-ion irradiation in permalloy films are much weaker and underline the importance of magnetostriction in the variation of the coercivity and anisotropy.