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.