Abstract:
This paper reports on a study of the effect of isotopic $^{16}$Î $\to$$^{18}$O oxygen substitution on the heat capacity and magnetocaloric properties of the La$_{0.7}$Ca$_{0.3}$MnO$_3$ manganite. Direct measurements of the magnetocaloric effect have demonstrated that, in La$_{0.7}$Ca$_{0.3}$MnO$_3$, the effect reaches a fairly large magnitude, but its temperature width is rather small. The $^{16}$Î ar $^{18}$Î isotopic substitution shifts the temperature of the maximum of the effect toward lower temperatures while leaving its magnitude practically unchanged. The magnetocaloric effect in the La$_{0.7}$Ca$_{0.3}$Mn$^{16}$O$_3$ + La$_{0.7}$Ca$_{0.3}$Mn$^{18}$O$_3$ sandwich structure has been measured by the direct method. It has been shown that fabrication of a sandwich from materials with close temperatures of the maxima of the magnetocaloric effect permits increasing the relative cooling power (RCP) compared with that of the starting materials.
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