Alternate coolants are needed to replace the use of increasingly scarce liquid helium, required, for instance, to cool the superconducting magnets used in medical resonance imaging. Magnetocaloric materials, with their entropically driven cooling power when cycled in a magnetic field, are such a replacement. The gadolinium-based garnets developed recently show amongst the largest magnetocaloric effects ; yet the cooling power of those materials peaks below 2 K, too low for many applications of liquid helium.



The aim of this PhD project is to find new rare-earth garnets with better magnetocaloric performances, by adequate substitutions on the three available cationic sites of the garnet structure. The project originality is the investigation of high-entropy garnet oxides to achieve this goal. The use of neutron scattering techniques will be a key asset to correlate chemical substitutions with changes in magnetic anisotropy and ground states in applied magnetic field, for an in-depth understanding of the key parameters controlling the magneto-caloric effect.