Magnetocaloric effect in (La1−xSmx)0.67Pb0.33MnO3 (0 ≤ x ≤ 0.3) manganites near room temperature

Abstract

We present an investigation on structure, magnetic and magnetocaloric properties of the perovskite manganites (La1−xSmx)0.67Pb0.33MnO3 (x = 0, 0.1, 0.2, 0.3) synthesized by sol–gel technique. The XRD patterns show that all synthesized samples have reflections typical of the perovskite structure with orthorhombic symmetry. Thermomagnetic measurements showed that all the samples display a paramagnetic–ferromagnetic transition with decreasing temperature. The Curie temperature decreases with increasing Sm content from 358 K for x = 0–286 K for x = 0.3. We determined the isothermal magnetic entropy changes of all the samples from the magnetization measurements and furthermore measured the adiabatic temperature change of the sample for x = 0.3 directly. The results showed that the adiabatic temperature change, determined using together the entropy change and the specific heat and the value obtained by direct temperature change measurements both give 1.3 K for a magnetic field change of 3 T at about 280 K. We also measured the cyclic adiabatic temperature-change of the sample and the results indicate that the sample undergoes a reversible temperature-change on field-cycling which is essential for magnetic refrigeration.