Accurate Estimation of $c$ -Axis Distribution and Order Degree of $L1_0$ Crystal in Magnetic Thin

The c-axis distribution and the accurate order degree of magnetic thin film with L10 structure are investigated by using a combination of out-of-plane and in-plane X-ray diffractions (XRDs). An L1₀ film formed on (001)-oriented underlayer or substrate includes a crystal of (001) orientation with the c-axis normal to the film surface and/or a crystal of (100) orientation with the c-axis lying in the film plane. An appearance of L1₀ superlattice reflection in either out-of-plane or in-plane XRD indicates a formation of L1₀(001) or L1₀(100) crystal. Accurate L1₀ order degrees of (001) and (100) crystals are calculated from the respective XRD data for FePt and FePd films. An accurate order degree of film total is estimated by taking into account the volume ratios of two types of L1₀ crystal. A simplified method for estimating order degree, where there are only two kinds of parameter, intensities of (001) and (002) reflections and lattice constant of c, is also proposed for typical L1₀ magnetic film materials of FePt, CoPt, FePd, MnAl, FeNi, FeAu, and FeRh. The order degree estimated by simplified method agrees with the accurate value within a small error of less than a few percentages.