Modification of Co/Pt multilayers by gallium irradiation - Part 1: The effect on structural and magnetic properties

Atomic force microscopy, transmission electron microscopy, optical, and mag neto-optical microscopy have been used to study how structural and magnetic properties are changed when a Co/Pt multilayer is quasihomogeneously irrad iated with Ga ions. Under low irradiation fluence, both grain size and text ure in the multilayer increase. These effects continue for fluences in exce ss of 1 x 10(15) Ga ions/cm(2), but beyond this dose significant thinning o f the multilayer is also observed. Three distinct irradiation-induced magne tic regimes with sharp transitions between each were identified. For Ga flu ences less than 5 x 10(12) ions/cm(2), the irradiated region retains perpen dicular uniaxial anisotropy but with coercivity lower than that of the as-g rown film. For fluences between 5 x 10(12) and 1 x 10(13) Ga ions/cm(2), a transition from perpendicular to in-plane magnetization was experienced. Ve ry little change of the in-plane magnetic properties of irradiated multilay ers is then observed until the sample experiences a ferromagnetic to parama gnetic transition at fluences around 1 x 10(15) Ga ions/cm(2). A brief comp arison with the effect of irradiating with He ions is given. (C) 2001 Ameri can Institute of Physics.