On the Curie temperature dependency of the magnetocaloric effect


We investigate the magnetocaloric effect dependency on the most important microscopic parameters of ferromagnetic materials, such as the Curie temperature (T-C), the spin value (J), and the magnetic field change (Delta H). Second- and first-order phase transition systems are considered, using the Bean-Rodbell model [A. Arrott, Phys. Rev. 108, 1394 (1957)] of magnetovolume interactions on the Weiss mean-field model [P. Weiss, J. Phys. Theory Appl. 6, 661 (1907)]. The magnetocaloric effect simulations show a surprising T-C(-2/3) linear dependence of the maximum entropy change (Delta Sm-max), which is observed for all simulated systems. An approximate state equation establishing the dependence of Delta Sm-max on T-C, Delta H, J, and the magnetic atoms density (N) is presented. The dependence of maximum magnetic entropy change on T-C(-2/3) is validated by a wide set of experimental results of second- and first-order phase transition materials that are promising for magnetic refrigeration applications at room temperature. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4726110]




Belo, JH; Amaral, JS; Pereira, AM; Amaral, VS; Araujo, JP

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Work partially supported by the projects PTDC/CTM-NAN/115125/2009 and FEDER/POCTI 155/94 from Fundaopara a Ciencia ex Tecnologia (FCT), Portugal. A. M. P. and J. S. A. thank FCT for the Grant (Nos. SFRH/BPD/63150/2009 and SFRH/BPD/63942/2009).

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