DF-05 Direct Measurement of the Rotative Magnetocaloric Effect of Anisotropic Magnetic Materials

The rotative magnetocaloric effect has gained popularity in the scientific community as an alternative to the direct magnetocaloric effect for an eventual implementation in simpler cooling devices [1]. Its appeal comes from the fact that one may use refrigeration schemes where the anisotropic active material rotates in a uniform field rather than moving in and out of a magnet to produce the cooling/warming cycles required for magnetic refrigeration, such as the one proposed by Balli et al. [2]. Since that proposal, several magnetic materials with very large anisotropy of the magnetic entropy change have been explored. However, few studies of the effect using direct measurements have been reported so far[3]. This study presents an experimental method to directly measure the temperature change of an anisotropic magnetic material as it rotates in a uniform magnetic field. The setup includes a thermometer attached to the sample that is suspended in a vacuum in a net with poor thermal conductance to the bath. As the sample rotates in a uniform field, its magnetic entropy varies, leading to cooling or warming depending on the direction of rotation between the easy and the hard magnetization axes. As shown in the figures, it enables the real-time monitoring of temperature changes as a function of various experimental controlling parameters such as the magnetic field, the angular velocity, and the direction of rotation. A model explaining most of the features observed will be presented alongside real-time direct measurements of ΔT for a TmMnO3 single crystal. * Work supported by the NSERC under grant RGPIN-2018-06656, CFREF, FRQNT and U. de Sherbrooke.References: [1] M. Balli et al., Appl. Phys. Rev., Vol 4, p.021305 (2017) [2] M. Balli et al., Appl. Phys. Lett., Vol 104, p.232402 (2014) [3] R. Almeida et al., J. Phys. Energy, Vol 6, p.015020 (2024)