“Treasure Maps” for Magnetic High-entropy-alloys from Theory and Experiment

The critical temperature and saturation magnetization for four- and five-component FCC transition metal alloys are predicted using a formalism that combines density functional theory and a magnetic mean-field model. Our theoretical results are in excellent agreement with experimental data presented in both this work and in the literature. The generality and power of this approach allow us to computationally design alloys with well-defined magnetic properties. Among other alloys, the method is applied to CoCrFeNiPd alloys, which have attracted attention recently for potential magnetic applications. The computational framework is able to predict the experimentally measured TC and to explore the dominant mechanisms for alloying trends with Pd. A wide range of ferromagnetic properties and Curie temperatures near room temperature in hitherto unexplored alloys is predicted in which Pd is replaced in varying degrees by, e.g., Ag, Au, and Cu. Since the revival of multi-principal element alloys more than ten years ago, hundreds of different high entropy alloys (HEAs) have been discovered.1 Among them are CoCrFeNi-based alloys such as CoCrFeNiMn and CoCrFeNiPd revealing superior mechanical2 and promising magnetic properties,3,4 respectively. Among other materials,5 the latter have been investigated as potential candidates for next-generation magnetic refrigeration applications.4 For that purpose, a Curie temperature, TC, close to room temperature is required which, unfortunately, is not fulfilled for CoCrFeNi alloys with TC near 100 K.1 Experiments indicate that additional alloying can change TC by several hundreds Kelvin, e.g., from 90 K for CoCrFeNiAl0.25 up to more than 500 K for CoCrFeNiPd2 alloys (see Fig. 1).3,6 Considering however the immense configurational space of these alloys, the optimization of TC into a narrow window close to room temperature—under the constraint of preserving other desirable properties—is a highly non-trivial task