Full-density recycled Nd-Fe-B sintered magnets were produced from collected waste Nd-Fe-B magnets with the coercivity, µ0Hc, of 1.30 T and remanence, µ0Mr, of 1.37 T. A small fraction of Nd6Dy21Co19Cu2.5Fe powder (Grain Boundary Modified (GBM™) powder) was blended to the powders obtained from the Nd-Fe-B waste magnets. The addition of 5.0 wt% GBM™ powder resulted in µ0Hc=2.36 T with µ0Mr=1.29 T in recycled magnets. The temperature coefficient of intrinsic coercivity, β, in the recycled magnet was measured to be -0.47 %/ o C. Microstructure studies showed that the addition of the GBM™ powder increases the volume fraction of a metallic Nd-rich phase in the recycled magnets. 3D tomography revealed a good interconnection of Nd-rich phases through the grain boundaries of the recycled magnet.Microstructure studies suggested that obtained high coercivity in the recycled magnet with 5.0 wt% addition of GBM™ is due to the formation of distinct grain boundary phase combined with the formation of Dy-rich shell in the Nd2Fe14B grains with 0.8 at. % Dy.

Magnetic refrigeration is an upcoming technology that could be an alternative to the more than 100‐year‐old conventional gas–vapor compression cooling. Magnetic refrigeration might answer some of the global challenges linked with the increasing demands for readily available cooling in almost every region of the world and the global‐warming potential of conventional refrigerants. Important issues to be solved are, for example, the required mass and the ecological footprint of the rare‐earth permanent magnets and the magnetocaloric material, which are key parts of the magnetic cooling device. The majority of existing demonstrators use Nd–Fe–B permanent magnets, which account for more than 50% of the ecological footprint, and Gd, which is a critical raw material. This work shows a solution to these problems by demonstrating the world's first magnetocaloric demonstrator that uses recycled Nd–Fe–B magnets as the magnetic field source, and, as a Gd replacement material, La–Fe–Mn–Si for the magnetocaloric heat exchanger. These solutions show that it is possible to reduce the ecological footprint of magnetic cooling devices and provides magnetic cooling as a green solid‐state technology that has the potential to satisfy the rapidly growing global demands.

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