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 magneto-optical microscopy have been used to study how structural and magnetic properties are changed when a Co/Pt multilayer is quasihomogeneously irradiated with Ga ions. Under low irradiation fluence, both grain size and texture in the multilayer increase. These effects continue for fluences in excess of 1 x 10(15) Ga ions/cm(2), but beyond this dose significant thinning of the multilayer is also observed. Three distinct irradiation-induced magnetic regimes with sharp transitions between each were identified. For Ga fluences less than 5 x 10(12) ions/cm(2), the irradiated region retains perpendicular uniaxial anisotropy but with coercivity lower than that of the as-grown 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. Very little change of the in-plane magnetic properties of irradiated multilayers is then observed until the sample experiences a ferromagnetic to paramagnetic transition at fluences around 1 x 10(15) Ga ions/cm(2). A brief comparison with the effect of irradiating with He ions is given