Abstract
Neutron-diffraction and magnetization measurements have been carried out on a series of samples of the magnetorefrigerant . 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 that has a similar shape for both increasing and decreasing field, with the maximum MCE exceeding —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 under optimal conditions.
- Received 20 July 2008
DOI:https://doi.org/10.1103/PhysRevB.79.014435
©2009 American Physical Society
Synopsis
Cooling with magnets
Published 28 January 2009
Scientists identify the microscopic origin of a record magnetocaloric effect in .
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