期刊
PHYSICAL REVIEW B
卷 79, 期 1, 页码 -出版社
AMER PHYSICAL SOC
DOI: 10.1103/PhysRevB.79.014435
关键词
crystal structure; entropy; ferromagnetic materials; germanium alloys; iron alloys; magnetisation; magnetocaloric effects; manganese alloys; neutron diffraction; paramagnetic materials; phosphorus alloys; refrigerants; solid-state phase transformations
资金
- National High Technology Research and Development Program of China [2007AA03Z458]
- Key Project of Science & Technology Innovation Engineering, Chinese Ministry of Education [705004]
- National Science Foundation graduate research program
- NSF [DMR-0703095]
Neutron-diffraction and magnetization measurements have been carried out on a series of samples of the magnetorefrigerant Mn1+yFe1-yP1-xGex. The data reveal that the ferromagnetic and paramagnetic phases correspond to two very distinct crystal structures, with the magnetic-entropy change as a function of magnetic field or temperature being directly controlled by the phase fraction of this first-order transition. By tuning the physical properties of this system we have achieved a magnetic-entropy change [magnetocaloric effect (MCE)] for the composition Mn1.1Fe0.9P0.80Ge0.20 that has a similar shape for both increasing and decreasing field, with the maximum MCE exceeding 74 J/kg K-substantially higher than the previous record. The diffraction results also reveal that there is a substantial variation in the Ge content in the samples which causes a distribution of transition temperatures that reduces the MCE. It therefore should be possible to improve the MCE to exceed 100 J/kg K under optimal conditions.
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