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MA: Fachverband Magnetismus

MA 51: Caloric Effects in Ferromagnetic Materials

MA 51.10: Talk

Friday, March 22, 2024, 12:15–12:30, H 2013

RCo2Hx magnetocaloric compounds for cryogenic gas liquefaction — •Allan Doering, Imants Dirba, Konstantin Skokov, and Oliver Gutfleisch — Technical University of Darmstadt, Darmstadt, Germany

Magnetic cooling, based on the magnetocaloric effect, is a new refrigeration technology that has been intensively developed for room temperature in recent decades. This technology could play also an important role at cryogenic temperatures to liquefy hydrogen, aiming for a future green economy and carbon-neutral societies. Typically, to use the magnetocaloric cycle, the hydrogen is pre-cooled with liquid nitrogen down to 77 K, and then magnetocaloric refrigeration is operated in the temperature range from 77 to 20 K to liquefy the H2 gas. Obviously, this new technology requires new materials. Since the maximum MCE takes place near the Curie temperature (TC), it is critical to use materials with a TC between 20 K and 77 K. The RCo2 family (where R stands for rare earth elements) are potential materials for this application due to their large MCE, however, some of these compounds have TC higher than 77 K. In our work, we tune TC of the RCo2 family to temperatures below 77 K using hydrogen as interstitial atoms. Samples were synthesized by arc-melting and annealed afterward. The quality of samples was determined by X-ray diffraction and scanning electron microscopy. Magnetization and heat capacity were measured to determine magnetocaloric effect of obtained alloys (magnetic entropy change and adiabatic temperature change. We acknowledge the HyLICAL and CRC 270 projects for the funding of this research.

Keywords: Magnetocaloric; Gas liquefation; Cryogenic; Hydrogenation