Multi-property Compositionally Complex Magnets for Advanced Energy Applications

The CoCoMag project proposes a novel concept for magnets materials design, applying compositionally complex alloys (CCA). By replacing the existing rare earth-based materials with multi-elements CCAs we will have a lower-cost material and a new class of magnetic alloys stabilized on the basis of entropy instead of enthalpy. The thermodynamic concept is relatively simple. An alloy that combines two pure elements A and B can either form a solid solution or intermetallic phases, governed by the thermodynamics of the Gibbs’ free energy. If the enthalpy of formation is negative, independent of the value of the entropy for the solid solution or intermetallic phase, the Gibbs’ free energy is negative and an intermetallic phase is formed. In the case that the enthalpy of formation is slightly positive, then a large total mixing entropy can make the Gibbs’ free energy negative, and new phases will be stabilized. The initial rationale behind this design concept is to maximize the total entropy of mixing, with the aim to stabilize novel solid solution or intermetallic phases. This approach expands the number of available magnetic alloys 10-fold thanks to the increasing of the number of degrees of freedom for structural and microstructural modifications. The project is focused on the formulation, synthesis, characterization and testing of novel rare earth-free materials for two applications: 1) permanent magnets, mainly applied in e-mobility sector; 2) magnetocaloric materials for the development of heat exchangers for magnetocaloric cooling. The success of CoCoMag initiative will allow to reduce the use of rare earth in magnetic materials manufacturing, mitigating the critical raw materials dependence of Europe and pushing the e-mobility and magnetocaloric cooling sectors.