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In the past 20 years, there has been a surge in research on the magnetocaloric response of materials, due mainly to the possibility of applying this effect for magnetic refrigeration close to room temperature. This review is devoted to the main families of materials suitable for this application and to the procedures proposed to predict their response. Apart from the possible technological applications, we also discuss the use of magnetocaloric characterization to gain fundamental insight into the nature of the underlying phase transition.

Articles you may be interested inComparison of the order of magnetic phase transitions in several magnetocaloric materials using the rescaled universal curve, Banerjee and mean field theory criteria J. Appl. Phys. 117, 17D144 (2015) The magnetocaloric effect in materials with a second order phase transition: Are T C and T peak necessarily coincident?

The universal character of the recent experimentally found master curve for the magnetic entropy change, S M , in studies of the magnetocaloric response of materials is analytically justified by using scaling arguments. The validity of the obtained scaling relations is checked against experimental data as well as the mean field and Heisenberg models. The curves are unique for each universality class. It is shown that the universal curve can be practically constructed in two different ways, reducing the number of required parameters with respect to the previous phenomenological derivation. This opens the possibility of an inexpensive screening of the performance of magnetocaloric materials, as it allows extrapolations to magnetic fields or temperatures not available in some laboratories.

The influence of different compositional modifications on the magnetic entropy change and refrigerant capacity of Finemet, Nanoperm, HiTperm, and bulk amorphous alloys is presented. For all the studied alloys, the field dependence of the magnetic entropy change exhibits a quadratic dependence in the paramagnetic regime, a linear dependence in the ferromagnetic temperature range, and a potential law with a field exponent ϳ0.75 at the Curie temperature. This exponent can be explained using the critical exponents of the Curie transition. It is shown that for alloys of similar compositional series, the magnetic entropy change follows a master curve behavior. © 2007 American Institute of Physics. ͓DOI: 10.1063/1.2709409͔Magnetic refrigeration is a field of current interest due to the enhanced performance and reduced environmental impact of these systems when compared with those based on the gas compression-expansion cycle. 1-3 Although current prototypes are based on rare-earth-based materials, 4 soft magnetic amorphous alloys have been recently proposed as low cost candidates for high temperature magnetic refrigeration. [5][6][7][8][9][10][11][12][13] Albeit the maximum magnetic entropy change, ͉⌬S M pk ͉, for these alloys is modest when compared to that of rareearth-based materials, 14,15 the remarkable difference in material costs is an incentive for studying their suitability as magnetic refrigerants. Besides their reduced magnetic hysteresis ͑virtually negligible͒, higher electrical resistivity ͑which would decrease eddy current losses͒, tunable Curie temperature and, in the case of bulk amorphous alloys, outstanding mechanical properties are beneficial characteristics for a successful application of the material. The field dependence of the magnetic entropy change ⌬S M in materials with a second order phase transition has also been recently studied, demonstrating that a master curve behavior is fulfilled for ⌬S M curves measured up to different maximum fields. 16 The aim of this work is twofold: to present a comparison of the relevant characteristics of the magnetocaloric response of selected Finemet, Nanoperm, HiTperm, and bulk amorphous alloys ͑BAAs͒ prepared in ribbon shape and to demonstrate that ⌬S M ͑T͒ curves of different alloys from the same compositional series can also collapse in a master curve.Amorphous alloys from different compositional series have been prepared in ribbon shape ͑ϳ25 m thick͒ by melt spinning: Fe x Co