Study on the origin of giant magnetocaloric effects using pulsed and steady high magnetic fields

2020 Fiscal Year Final Research Report

• Project/Area Number: 18K13979
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 26010:Metallic material properties-related
• Research Institution: Tohoku University
• Principal Investigator: Kihara Takumi 東北大学, 金属材料研究所, 助教 (80733021)
• Project Period (FY): 2018-04-01 – 2021-03-31
• Keywords: 磁気冷凍 / 磁気熱量効果 / ホイスラー合金 / パルス強磁場 / 比熱

Outline of Final Research Achievements

Ni-Mn-based Heusler alloys Ni-Mn-Z (Z = Ga, In, Sn, and Sb) have been studied extensively as a class of promising magnetocaloric materials. These materials undergo a first-order martensitic transformation accompanied by the metamagnetic phase transition. In this study, the magnetocaloric effects were measured directly as the adiabatic temperature change using the pulsed high magnetic fields. By combining magnetization, specific heat, magnetostriction, and microscopy measurements under pulsed and steady high magnetic fields, we evaluated quantitatively the electronic, magnetic, and lattice entropy. First-principle based calculations revealed that certain non-stoichiometric compositions can show a giant magnetocaloric effect attributable to the electronic entropy change.

Free Research Field

磁性

Academic Significance and Societal Importance of the Research Achievements

磁気冷凍は気体冷凍に代わる次世代冷凍技術として高い注目を集めているが、これまでに発見された磁気冷凍材料の多くは磁場誘起構造相転移に伴う格子エントロピー変化を活用していたため、一次相転移特有の大きな磁場ヒステリシスによってエネルギーロスが発生するという問題があった。本研究によって、電子エントロピー変化を用いた新しい磁気冷凍材料開発の道が示された。これにより一次相転移への拘りはもはや不要となり、今後ヒステリシスによるエネルギーロスの問題を解決する可能性がある。