Shape induced in-plane magnetic anisotropy reorientation in epitaxial hexagonal close packed cobalt dots

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Abstract
The in-plane magnetic easy-axis reorientation was investigated for the arrays of (10⋅0) hcp Co rectangular dots 0.2 μm in width with a variable length from 3 to 5 μm perpendicular to the c axis. In the system, the magnitude of the shape anisotropy contribution is determined by a lateral aspect ratio of the dot, while the magnetocrystalline anisotropy contribution is temperature dependent. The torque curves for the dot arrays exhibited a characteristic fourfold symmetry due to the easy-axis reorientation. The reorientation angle from the initial easy axis was found to be dependent on the value of in-plane demagnetization factors as well as the temperature variable first and second magnetocrystalline anisotropy constants. The experimental results are in good agreement with the calculated effective magnetic anisotropy.