Large reversible magnetocaloric effect of the EuAl3Si single crystal

The magnetic properties, magnetocaloric effect and magnetoresistance of EuAl3Si single crystal have been investigated. A giant reversible magnetocaloric effect was observed around TC = 14.5 K. For the low magnetic field changes of 0-2 T, the maximum values of magnetic entropy change and refrigerant capacity are 13.4 J/kg K, and 166 J/kg,respectively, with the corresponding adiabatic temperature of 7.2 K.These excellent magnetocaloric parameters suggest EuAl3Si as a promising candidate for magnetic refrigeration application around liquid hydrogen temperature

Viable Materials with a Giant Magnetocaloric Effect

This review of the current state of magnetocalorics is focused on materials exhibiting a giant magnetocaloric response near room temperature. To be economically viable for industrial applications and mass production, materials should have desired useful properties at a reasonable cost and should be safe for humans and the environment during manufacturing, handling, operational use, and after disposal. The discovery of novel materials is followed by a gradual improvement of properties by compositional adjustment and thermal or mechanical treatment. Consequently, with time, good materials become inferior to the best. There are several known classes of inexpensive materials with a giant magnetocaloric effect, and the search continues

データ駆動による磁気冷凍材料の発見と材料開発を加速するXRD自動解析システムの構築

筑波大学University of Tsukuba博士（工学）Doctor of Philosophy in Engineering2022doctoral thesi

Exploring magneto- and multicaloric materials for room and cryogenic temperature applications

A future sustainable society requires energy-efficient and environmentally friendly technologies to successfully tackle the challenges of climate change, population growth, and a rising standard of living. The significance of cooling for society emphasizes the need to find efficient and environmentally friendly refrigeration alternatives. Solid-state caloric cooling represents such an alternative technology. In this thesis, Ni(-Co)-Mn-Ti all-d Heusler alloys, Fe₂AlB₂-type MAB phases, La(Fe,Si)₁₃-type compounds, and the novel Co₄(OH)₆(SO₄)₂[enH₂] organic-inorganic hybrid material are explored for magneto- and multicaloric cooling applications at room and cryogenic temperatures. Concerning room temperature applications, Ni(-Co)-Mn-Ti all-d Heusler alloys are optimized and comprehensively investigated. As a result, very high isothermal entropy changes are achieved in moderate magnetic fields and record-breaking adiabatic temperature changes are reported in high magnetic fields. However, hysteresis is identified as the main obstacle, limiting the caloric performance under cyclic conditions. Fe₂AlB₂-type MAB phases do not exhibit hysteresis and are therefore investigated as low-criticality and low-cost alternatives, showing small to moderate magnetocaloric effects around room temperature. At cryogenic temperatures, a multicaloric cooling approach with isotropic pressure and magnetic field as external stimuli is investigated, using a low-criticality and low-cost La₀.₇Ce₀.₃Fe₁₁.₆Si₁.₄ compound. This approach, though challenging to technically implement, achieved high isothermal entropy changes at natural gas, oxygen, and nitrogen liquefaction temperatures. In combination with adiabatic temperature change measurements of Ni-Co-Mn-Ti all-d Heusler alloys, universal limitations of hysteretic first-order phase transition materials are revealed for hydrogen liquefaction applications, directing the search for suitable candidates to second-order phase transition materials. Following this guideline, the novel compound Co₄(OH)₆(SO₄)₂[enH₂] shows the highest isothermal entropy changes of any rare-earth-free material for magnetocaloric hydrogen liquefaction so far. In general, it is demonstrated that caloric cooling technology, particularly at cryogenic temperatures, has great potential to contribute to carbon-neutrality and energy-efficiency in pursuit of a sustainable future