Magnetic properties of Ho-Co, Dy-Co, and Gd-Fe amorpous films prepared by dual-source evaporation

The room temperature magnetic properties of evaporated amorphous Ho-Co, Dy-Co and Gd-Fe thin films are reported. The magnetization data are fitted using a mean field model and the exchange constants and atomic magnetic moments are determined. All three alloy systems exhibit uniaxial anisotropy normal to the plane of the film and stripe domains are observable on some samples. The anisotropy energies are found to be within the following values over the composition ranges studied: Ho-Co, 4 × 10⁴-3.5 × 10⁵ergs/cm³; Dy-Co, 4 × 10⁵-2.8 × 10⁶ergs/cm³Gd-Fe, 2 × 10⁵-6 × 10⁵ergs/cm³. The anisotropy data for each alloy system are fitted with a dipolar equation Ku=ΣCijMiMjwhere Cijis a dipolar coupling constant for the i-j pair, and Miand Mjare sublattice magnetizations. The implications of these results with respect to a pair ordering mechanism as the cause of the anisotropy are discussed.