Magnetocaloric effect of high-entropy GdTbDyHoEr-based alloys: Ribbons, powders, and films

The magnetocaloric effect is the reversible temperature change of a magnetic material upon the application or removal of a magnetic field. Recently, one of the directions of development of new efficient magnetocaloric materials has been advancing taking into account the concept of high-entropy alloys (HEAs). Within this approach, five or more metallic components, taken in equal mole fractions, can form a single-phase crystalline alloy where atoms of different types are randomly arranged at the lattice sites. A HEA is a disordered substitutional solid solution, lacking long-range order for each atomic type. The disordered arrangement of all atoms at the lattice sites leads to an increase in the configurational entropy of such a material. Research into the magnetocaloric properties of HEAs based on heavy rare earth elements, which began relatively recently, has demonstrated the potential for their use in magnetic refrigerators. It should be noted that the efficiency of a magnetic refrigerator is determined not only by the composition but also by the form of the working material. This review provides the results of the comparative analysis of the available results devoted to a study of the features of the crystal structure, magnetic and magnetocaloric properties of high-entropy GdTbDyHoEr type alloys in a bulk state, as well as in the shape of rapidly quenched ribbons, powders, and thin films.