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تسجيل مستخدم جديدMagnetocaloric properties of an inhomogeneous magnetic thin film of 7.6 nm La${}_{0.7}$Sr${}_{0.3}$MnO${}_{3}$ grown on SrTiO${}_{3.}$
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Magnetocaloric properties of an inhomogeneous magnetic system of a 7.6 nm La${}_{0.7}$Sr${}_{0.3}$MnO${}_{3}$ consisting of superparamagnetic (SPM) with blocking temperature ( $T_B$ = 240 K) and ferromagnetic (FM) phases ( $T_C$ = 290 K) is studied by dc magnetization measurements. Isothermal magnetization versus applied magnetic field is carried out from 100 K to 320 K in magnetic fields up to 4 kOe to determine changes in the magnetic entropy ($-Delta S_M$) and the relative cooling power (RCP). Due to the co-existence of SPM and FM phases, there are two peaks in the temperature dependence of$-Delta S_M$ in different applied magnetic fields from 1.3 kOe to 4 kOe. The peaks are at 220 K and 270 K which are close $T_B$ and $T_C$ of the film. The highest RCP occurs at 270 K (which is in $T_B$ $mathrm{<}$ $T$ $mathrm{<}$ $T_C$) in H = 4 kOe with the value of 0.19 (J/kg K). The $-Delta S_M$ vs T data are fit to the exponent power law, $-Delta S_M=a H^n$ where it shows good fits for the whole measured temperature range. This analysis reveals a deviation of n from $n$ = 2/3 which is likely due to the presence of SPM spin clusters in the dead layer for $T$ $mathrm{<}$ $T_C$. Results show that the thin film of La${}_{0.7}$Sr${}_{0.3}$MnO${}_{3}$ can be a good candidate for magnetic refrigeration devices with multiple RCP peaks in low and high temperatures.
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