Entropy and magnetocaloric effects in ferromagnets undergoing first- and second-order magnetic phase transitions
The exchange striction model is invoked to derive an expression for the entropy of ferromagnetic materials undergoing first- and second-order magnetic phase transitions. The magnetocaloric and barocaloric effects are calculated for the ferromagnet La(Fe{sub 0.88}Si{sub 0.12}){sub 13} undergoing a first-order phase transition. The calculated results are in fair agreement with experimental data. The ferromagnet La(Fe{sub 0.88}Si{sub 0.12}){sub 13} is used as an example to predict the changes in magnetic and magnetocaloric properties associated with gradual increase in the magnetoelastic coupling constant (i.e., with passage from first- to second-order magnetic transition region). It is shown that stronger magnetoelastic coupling leads to stronger magnetocaloric effects and changes their dependence on magnetic field and pressure. Expressions are obtained for the maximum field- and pressure-induced entropy changes. An analysis is presented of the mechanism responsible for the increase in magnetocaloric and barocaloric effects associated with change from the second- to first-order magnetic phase transition.
- OSTI ID:
- 21246947
- Journal Information:
- Journal of Experimental and Theoretical Physics, Journal Name: Journal of Experimental and Theoretical Physics Journal Issue: 2 Vol. 108; ISSN JTPHES; ISSN 1063-7761
- Country of Publication:
- United States
- Language:
- English
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