High magnetic field induced pillar growth and subsequent magnetic properties of the thermal evaporated Co thin films

•Large magnetic force induces Co particles grow in a pillar mode.•Pillars favor to aggregate a large one (1.5 μm in diameter) in high magnetic field.•Pillar structure influences the in- and out-of-plane magnetic anisotropy.•Co film is difficult to be magnetized to saturation due to the pillar structure.

This letter studies the effects of in-situ high magnetic field application on the Co film growth via thermal evaporation. It was found that the crystalline structures of Co films were not changed by the application of the 6 T magnetic field. However, high magnetic field induced the Co particles to grow in a pillar mode and align along the magnetic field direction. Furthermore, the pillars prefer to aggregate to a large one (about 1.5 μm in diameter) under the high magnetic field condition. The in- and out-of-plane magnetic anisotropy was significantly influenced by the pillar structure and the film was difficult to be magnetized to saturation due to the pillar structure.