Control of in-plane uniaxial anisotropy of CoPd-CaF₂ nanogranular films by tandem-sputtering deposition

In-plane uniaxial anisotropic CoPd-CaF₂ nanogranular soft magnetic films for gigahertz applications were prepared using RF tandem-sputtering deposition with substrate revolution. Strong anisotropy with a large anisotropy field exceeding 50 kA/m was achieved in the centrifugal-centripetal direction of the substrate revolution, regardless of the presence or absence of an applied external dc field for induced anisotropy. X-ray pole-figure analysis demonstrated that the crystalline orientation of CoPd111 as a crystallographically magnetic easy axis corresponds to the easy axis of the films. Thus, the soft magnetic properties and uniaxial anisotropy of nanogranular films are determined by both random-magnetocrystalline and shape anisotropies. Complex permeabilities indicated high ferromagnetic resonance frequency exceeding 5GHz with a low Gilbert damping factor of 0.06 for the nanogranular films, and the applied field caused a change in the damping factor. Thus, the magnetic properties of the films can be controlled by the substrate motion and the applied field under tandem-sputtering conditions.