Asaya Fujita1
AIST Chubu1
Among various types of caloric phenomena, magnetocaloric effect is relatively easy to control in a non-contact external field, and therefore, external-field sources are installed by keeping thermal insulation from the heart of the thermal cycle. Meanwhile, attenuation of magnetic flux according to the Coulomb law leads to “gigantic” scales in both the size and cost of the magnetic field generators, such as the electromagnetic or permanent-magnet circuits. For the portability and cost-reduction of the magnetic heat-pump systems, a central issue imposed on materials is a compatibility between realization of highly sensitive magnetocaloric response against smaller magnetic fields, and superior workability for forming compact and efficient beds.<br/>Our recent benchmark in an isothermal entropy change △S<sub>M</sub> reaches about 20 J/kg K under 1 T for (La,Pr)(Fe,Mn,Si)<sub>13</sub>H compounds around 300 K. However, in the active magnetic regenerator (AMR)-type system, which is considered as a most viable technology, no isothermal process is incorporated but only iso-field and adiabatic temperature changes construct the heat cycle. Accordingly, the critical metrics are amount of latent heat η under (even) zero magnetic field and a span of adiabatic temperature change △T<sub>ad</sub>. In this work, we will introduce recent achievements in the materials design, in addition to the theoretical aspect, to improve and analyze η and △T<sub>ad</sub>. We also evaluate the durability of magnetocaloric performance against various fabrication techniques of the bed with integrated microchannel structures. In this regard, careful attention must be paid on the metallographic aspects such as the peritectic reaction in phase diagram, and affinity for (contaminating) light elements. We will discuss the advantages and disadvantages of each method for the bed fabrication.