Abstract
In this paper, we have studied the magnetic and magnetocaloric properties of the perovskite manganites La0.67Pb0.33−x Ag x MnO3 (0≤x≤0.15), which show a sharp paramagnetic-ferromagnetic phase transition over a wide temperature range (T=250–401 K). The Curie temperature has been analyzed by two methods: using the numerical derivative dM/dT and the thermodynamic model. The experimental results indicate that T C decreases from 368 to 288 K with increasing Ag substitution independently of the method used to obtain T C. Upon 10 KOe applied magnetic field, the large magnetic-entropy change (|ΔS M|) reaches values of 2.75, 3, 3.25 and 3.5 J/kg K for x=0, 0.05, 0.10 and 0.15 compositions, respectively, which are comparable to that of Gd. The relative cooling power (RCP) increases with increasing Ag content from 68.75 (x=0) to 156.27 J/kg (x=0.15) for ΔH=10 KOe. Through these results, La0.67Pb0.33−x Ag x MnO3 materials are strongly suggested for the use of active refrigerants for magnetic refrigeration technology near room temperature.
Highlights
Magnetic refrigeration based on the magnetocaloric effect (MCE) is a viable and competitive cooling technology in the near room-temperature region and it has recently attracted much research interest due to its potential advantage of environmental friendliness over conventional gas refrigeration [1, 2], such as high energy efficiency, less environmental stress, and small volume [3,4,5]
When a magnetic field is applied to a magnetic material, which is thermally isolated from its surroundings, a change of the temperature of the solid may be observed
We investigate the magnetic and magnetocaloric effect related to the effects of Ag doping in La0.67Pb0.33−x Agx MnO3, which can be a suitable candidate as a working substance in magnetic refrigeration near room temperature
Summary
Magnetic refrigeration based on the magnetocaloric effect (MCE) is a viable and competitive cooling technology in the near room-temperature region and it has recently attracted much research interest due to its potential advantage of environmental friendliness over conventional gas refrigeration [1, 2], such as high energy efficiency, less environmental stress, and small volume [3,4,5]. When a magnetic field is applied to a magnetic material, which is thermally isolated from its surroundings, a change of the temperature (heating or cooling) of the solid may be observed. The Curie temperature of Gd5Si2Ge2 is about 276 K, which is much lower than that of Gd of 294 K, making this alloy difficult to be used in room-temperature magnetic refrigerators [11] For this reason, there is an extensive search of new materials suited for solid-state cooling machines working in this temperature range, such as Ni–Mn–Ga alloys [12], Mn–As–Sb alloys [13], La–Fe–Co–S alloys [14], Mn–Fe–P–As alloys [15] and various compounds of manganites [5]. We investigate the magnetic and magnetocaloric effect related to the effects of Ag doping in La0.67Pb0.33−x Agx MnO3, which can be a suitable candidate as a working substance in magnetic refrigeration near room temperature
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