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Enhanced Magnetocaloric Effect Driven by Hydrostatic Pressure in Na-Doped LaMnO₃

Author:
Das, Rajasree, Midya, Arindam, Kumari, Mukesh, Chaudhuri, Anindita, Yu, Xiaojiang, Rusydi, Andrivo, Mahendiran, Ramanathan
Source:
Journal of physical chemistry 2019 v.123 no.6 pp. 3750-3757
ISSN:
1932-7455
Subject:
X-ray absorption spectroscopy, ambient pressure, entropy, hydrostatic pressure, magnetic fields, manganese, physical chemistry, specific heat, spectral analysis, temperature, thermal expansion
Abstract:
We compare the impact of hydrostatic pressure on the magnetic and magnetocaloric properties in monovalent alkali earth ion-doped polycrystalline La₁–ₓNaₓMnO₃ (x = 0.05, 0.10). X-ray absorption spectra of Mn L₃,₂ edges reveal the presence of Mn⁴⁺ in these doped ferromagnetic samples. Ferromagnetic Curie temperature (TC) obtained from the temperature dependence of magnetization is 249.7 K for the x = 0.05 and 269.6 K for x = 0.1 samples in ambient pressure. A magnetic field change of 3T causes an adiabatic temperature change of ΔTₐd = 2.8 and 2.0 K for x = 0.05 and 0.1, respectively, at their respective TCs. On the other hand, application of 1.1 GPa hydrostatic pressure not only causes a huge shift in TC toward higher temperature (ΔTC ≈ 17.9 and 16.3 K for x = 0.05 and x = 0.1, respectively) but also enhances total entropy change (ΔS) for x = 0.1, while not affecting ΔS for x = 0.05. Specific heat and linear thermal expansion coefficient measurements suggest a possibility of structural transition below the paramagnetic–ferromagnetic transition in x = 0.1, which is absent in x = 0.05. Pressure-driven enhancement of structural transition temperature could be a possible origin of the enhanced magnetocaloric effect in x = 0.1.
Agid:
6309962