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A compilation of magnetocaloric properties of metallic nanostructures with Curie temperature (TC) between 260 and 340 K has been tabulated. The tabulated data show that nanostructure plays an important role in enhancing the magnetocaloric properties of a material, namely by reducing the peak of magnetic entropy, but broadening of the magnetocaloric effect curve with an average of 10 K sliding window for Curie temperature. A second table lists all bulk metallic and intermetallic materials, in which there is no nanostructural data, with an entropy change of at least 20 J/kg K and a Curie temperature between 260 and 340 K. We propose that further experiments should be made on the nanostructured form of these materials. [ABSTRACT FROM AUTHOR]

A new experimental characterization is presented of time-, field-, and temperature-dependent dynamic effects in magnetization of a nanocomposite which displays slow decay. Field and temperature variations of irreversible susceptibility, χirr, decay coefficient,S, fluctuation field,hf, and activation volume,V, have been calculated for the nanocomposite sample (Co80Ni20) using a recently developed modified Preisach–Arrhenius (MPA) model. The sample is composed of non-interacting nanoparticles having negligible reversible magnetization. Non-Arrhenius behavior is observed in both the maximum decay coefficient,Smax, and the fluctuation field,hf, as a function of temperatureT.The peak of both temperature curves are identical and occur at a critical temperatureTkof ∼50 K, which agrees with our experimental results. Based on the effect of a temperature-dependent chemical potential on energy barrier,hfis studied forT

The adiabatic temperature change (ΔTad) during the magnetization process of polycrystalline gadolinium and Ni51Mn33.4In15.6Heusler alloy is directly measured near the Curie temperature. The cooling factor (CF) is introduced as the area under the curve of adiabatic temperature change versus ambient temperature. The CF provides more representative measure of cooling performance in the operational temperature range. Selecting different temperature abscissas qualitatively changes the interpretation of the cooling performance of a magnetocaloric material. In particular, plotting ΔTadversus initial temperature gives a measurably different CF compared to that given by plotting ΔTadversus average temperature. [ABSTRACT FROM AUTHOR]