Development of sustainable intermetallic iron-based gap magnets for automotive applications

Rare-earth (RE) permanent magnets are of fundamental importance in the transition from fossil fuels towards renewable energy alternatives since they are used in a variety of technological applications, in particular electric motors and generators. In the last decade, more concerns have been raised regarding the supply risks of RE, their volatile prices and environmental impact. The development of a new class of noncritical magnets with intermediate properties, called “gap magnets”, could help reducing the demand for such critical materials. Since iron is extremely abundant, iron-based materials are desirable for this new class of magnets. In this work, we have synthesized and characterized the intrinsic properties of two families of intermetallic iron-based magnetic materials, namely Fe5SiB2 and Fe2P. Optimization of intrinsic properties is a key step for applications, since high Curie temperature allows higher working temperatures and MS and HA are the theoretical upper limits for remanence and coercivity, respectively. Intrinsic properties can be tuned by chemical substitution, thus, we synthesized different samples of Ge, Re and Cr doped Fe5SiB2 and Co and Si co-doped Fe2−xCoxP1−ySiy. Experimental results on the Fe2P system have also been complemented by theoretical DFT calculations in order to estimate magnetic properties such as magnetic moment and magnetocrystalline anisotropy energy. Results show that, despite increased anisotropy, doped Fe5SiB2 system remains a semi-hard magnet, but Fe2−xCoxP1−ySiy has great potential as gap magnet, with theoretical maximumenergy product approaching 200 kJ/m3.