First-principles investigation of high-entropy magnetic recording media

Recent progresses in multi-element alloys with high configurational entropy offer an exciting new arena to realize novel types of high anisotropy materials.1 In this work, we combine transition metal elements to design optimized high entropy alloys (HEAs) with high magnetic anisotropy energy (MAE) and moderate Curie temperature (Tc) towards applications in magnetic recording media.

We have used the “Questaal” package, owing to its incorporation of Coherent Potential Approximation (CPA), to study an equiatomic [FeCoCuMnNi]_0.5Pt_0.5 system, a L10-phase. The crystal has a stable ordered phase of body-centered tetragonal (BCT) lattice formed by five transition-metal elements randomly occupying the corner sites, while a Pt atom resides at the center. MAE of the equiatomic phase is found to be 1.28 meV per unit cell using LSDA functional. We have further explored the trend of MAE by varying the amount of five transition metal elements with certain constraints such that 50% of L10-phase system consist of [FeCoCuMnNi] while the central Pt-atom remains the same. Similarly, we have investigated the Curie temperature (Tc) when quantity of individual atoms in [FeCoCuMnNi] is changed under certain constraints. GGA and LDA+U functionals are also tested to corroborate the results with experiments. The extremely large parameter space emanated from constrained combination of 5 transition elements makes it logical to use some machine learning algorithm to detect any specific trend in MAE, Tc, and both. Our results show a promising approach toward achieving optimized HEA material with large MAE and moderate Tc, suitable for magnetic recording media applications.