Magnetocaloric Materials Group

Our group aims to discover magnetocaloric materials for the hydrogen-liquefaction active magnetic regenerator (AMR) developed in NIMS. Among material requirements, the most important one is a large entropy change, ΔS, induced by application of magnetic field.
It is desirable that the entropy change reaches ΔS = 0.1 — 0.3 J/K cm3 under the magnetic field of 4 T in the temperature range between -200℃ and -250℃, which are the boiling points of nitrogen and hydrogen, respectively. The entropy change is so enormous that it is hard to achieve in a paramagnetic state or via a conventional second-order magnetic transition. Thus, our primal target is the materials showing a first-order magnetic transition like itinerant metamagnetic transition which can generate a large entropy change.

Research field and subjects

Researching themes

1. Magnetic alloys
Currently, various alloys, such as Hustler alloy, Laves phase alloy and La(Fe,Si)13, are known to show excellent magnetocaloric effects (MCE) at various temperatures. To adjust the temperatures to the ones suitable for the hydrogen liquefaction and to improve their MCE we have tested substitutions of their elements in addition to the effort to discover a new family of alloys with good MCE. Furthermore, we have tried to solve potential problems like cycle fatigue in actual use of the alloys.

2. Magnetic ceramics and others
The materials showing first-order magnetic transitions are not limited to the alloys. We have searched for a candidate also among ceramics, 3d transition-metal sulfides, and so on. Some of them are rare-earth free or contain reduced amount of rare earth elements. Such materials are paid special attention because of their advantage for cost saving.

3. Electronic properties
We have performed more fundamental study of electronic properties. For example, electronic band structures of metamagnetic materials are elucidated by measurements of quantum oscillation and photoelectron spectroscopy. Magnetic properties of Mott insulators are investigated by muon spin rotation and nuclear magnetic resonance. The scientific understanding of the electronic properties will certainly lead to discovery of novel magnetocaloric materials through new ideas and concepts.

Inquiry about this page

Magnetocaloric Materials Group
1-1 Namiki, Tsukuba, Ibaraki, 305-0044 JAPAN
TEL. +81-29-860-4610
FAX. +81-29-852-7449
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