Abstract
The method based on low-field microwave absorption measurements is presented to estimate the relative change of entropy with magnetic field. This method is illustrated on both the polycrystalline Gd5Si2Ge2 alloy and the single crystalline La0.7Ca0.3MnO3 manganite. It is shown that there is the simple functional relation between magnetization and non-resonant absorption over a narrow temperature range near the magnetic phase transition. The magnetoresistance is assumed to be the dominating mechanism underlying this relation.
Highlights
Since discovery of the colossal magnetocaloric effect (MCE) in Gd5Si2Ge2,1 a great interest has been attracted to the magnetic refrigeration technology offered as an energy-efficient and environment-friendly alternative for the usual vapor-cycle refrigeration
First of all they should have as big as possible the values of both adiabatic temperature change Tad and isothermal magnetic entropy change S as well as the relative cooling power parameter RC P = − SδT f whm, where δT f whm is the full width at half maximum of the − S(T) curve
Besides magnetocaloric properties, these materials should have close to zero coercivity, small thermal hysteresis, small specific heat, large thermal conductivity and resistivity, low cost of preparation, stability, simple sample synthesis
Summary
Since discovery of the colossal magnetocaloric effect (MCE) in Gd5Si2Ge2,1 a great interest has been attracted to the magnetic refrigeration technology offered as an energy-efficient and environment-friendly alternative for the usual vapor-cycle refrigeration. On the estimation of the magnetocaloric effect by means of microwave technique Pavlo Aleshkevych Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, 02-668, Warsaw, Poland (Received 15 July 2012; accepted 12 October 2012; published online 22 October 2012)
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