Determination of Crystallographic Phase and Estimation of Order Degree for Rare Earth-Transition Metal Alloy Films with Hexagonal Structures

Abstract

A magnetic alloy film consisting of rare earth (R) and transition (T) metals with hexagonal structure may involve crystallographic phases such as R2T17, R2T7, and RT3 in addition to RT5 phase. The structures of hexagonal R-T films with the c-axis parallel and perpendicular to the substrate surface are characterized by employing a combination of reflection high-energy electron diffraction (RHEED) and X-ray diffraction (XRD). The crystallographic phase is identified by analyzing a reciprocal lattice map measured by RHEED. The degree of RT5 ordering is estimated by comparing XRD data (intensity, structure factor, Lorentz-polarization factor, and absorption factor) of ( 0001) superlattice and (0002) fundamental reflections (conventional method). A simplified method for estimating the order degree, where only the intensity ratio of ( 0001) to (0002) reflection is considered, is proposed for some of the typical RT5 film materials of SmCo5, PrCo5, YCo5, etc. The order degree estimated by employing the simplified method agrees in a small error less than a few percentages with that calculated using the conventional method.