Magneto-optical measurement of anisotropy energy constants on amorphous rare-earth transition-metal alloys

Measurements of the magneto-optic polar Kerr effect are performed on samples with perpendicular magnetization using in-plane magnetic fields. The magnetic anistropy constants are then determined from these measurements. The applied in-plane magnetic field varies from -20 to 20 kOe. Samples are mounted in a temperature-controlled chamber whose temperature is varied in the range of 80-475 K. In the theoretical model the anisotropy energy is expressed as the sum of terms containing sin² φ and sin⁴ φ with two anisotropy constants, K₁ and K₂, to be determined. By matching the theoretical curves with the experimental data, we obtain two functions α(T) and β(T), which are the normalized values of K ₁(T) and K₂(T) with respect to the saturation magnetization M_s(T).