A. Fujita, Tohoku University, Sendai, Japan; K. Fukamichi, Tohoko University, Sendai, Japan
Recently, magnetic refrigeration has attracted much attention as an alternative technology to gas-vaporization cooling. We have developed excellent magnetic refrigerant materials from La(FexSi1-x)13 which exhibit large magnetocaloric effects such as an isothermal magnetic entropy change ŢSm and an adiabatic temperature change ŢTad. These values are obtained around the Curie temperature TC = 195 K. However, the value of TC is increased by expanding the lattice constant. For practical applications, therefore, hydrogenation is carried out in order to use such large values of magnetocaloric effects in the vicinity of room temperature. By controlling hydrogen content, we can obtain a wide working temperature range while keeping large values of ŢSm and ŢTad. Therefore, La(FexSi1-x)13 and its hydrides are promising as magnetic refrigerants working at wide temperature ranges covering room temperature.
Summary: La(FexSi1-x)13 compounds exhibit large magnetocaloric effects due to the first-order magnetic phase transition induced by relatively low applied magnetic fields just above the Curie temperature TC. To apply these compounds to magnetic refrigerants working around room-temperature, TC is controlled from about 185 to 340 K by hydrogen absorption.
