Large magnetocaloric effect and critical behavior in Cu-doped nanocrystalline La0.7Te0.3Mn1-yCuyO3 (0.1 ≤ y ≤ 0.5)

• Published in: Vacuum 2019-11, Vol.169, p.108943, Article 108943
• Main Authors: Meenakshi, Kumar, Amit, Mahato, Rabindra Nath
• Format: Article
• Language: English
• Subjects: Critical exponents; Magnetic entropy; Manganites; Sol-gel
• ISSN: 0042-207X; 1879-2715
• DOI: 10.1016/j.vacuum.2019.108943

The impact of copper doping on the magnetic properties and critical behavior of the nanocrystalline La0.7Te0.3Mn1-yCuyO3 (0.1 ≤ y ≤ 0.5) system has been explored. The powder X-ray diffraction (XRD) patterns affirmed the single crystal phase for all samples without any detectable secondary phase. We have observed rhombohedral (R3‾c space group) crystal symmetry for y ≤ 0.3. With the increase in copper doping composition (y = 0.4 and 0.5) structure changes to orthorhombic (Pbnm space group). The temperature-dependent magnetization data suggests a paramagnetic (PM) to ferromagnetic (FM) phase transition upon cooling for all compositions. The Curie temperature TC is almost constant (about 226 K) for the compositions y ≤ 0.3 and after that TC decreases from 154 K (y = 0.4) to 91 K (y = 0.5). The maximal values of magnetic entropy change |ΔSMmax| were obtained from a series of magnetic isotherms and were observed to be 4.59 J/(kg-K), 4.84 J/(kg-K), 3.92 J/(kg-K), 2.49 J/(kg-K) and 1.56 J/(kg-K) for y = 0.1, 0.2, 0.3, 0.4 and 0.5 respectively up to a field change of 5 T. The critical behavior at PM-FM transition for all the samples was studied and reliability of the obtained critical exponents was checked using scaling hypothesis. The critical exponents deduced in this study were observed to follow the mean field, 3D Ising and 3D Heisenberg model. •The nanocrystalline La0.7Te0.3Mn1-yCuyO3 (0.1≤y≤0.5) samples show paramagnetic-ferromagnetic phase transition upon cooling.•Arrott plots, Franco’s universal curves, and Landau theory reveal a second-order magnetic phase transition.•The magnetic entropy change has been calculated from Maxwell relation and Landau theory.•Critical exponents has been derived using the field dependence of maximum magnetic entropy change.•Reliability of the critical exponents was checked using the scaling theory.