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

Abstract

We compare the impact of hydrostatic pressure on the magnetic and magnetocaloric properties in monovalent alkali earth ion-doped polycrystalline La 1−x Na x MnO 3 (x = 0.05, 0.10). X-ray absorption spectra of Mn L 3,2 edges reveal the presence of Mn 4+ in these doped ferromagnetic samples. Ferromagnetic Curie temperature (T C ) 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 ΔT ad = 2.8 and 2.0 K for x = 0.05 and 0.1, respectively, at their respective T C s. On the other hand, application of 1.1 GPa hydrostatic pressure not only causes a huge shift in T C toward higher temperature (ΔT C ≈ 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.

Expansion of the multifunctionality in off-stoichiometric manganites using post-annealing and high pressure: physical and electrochemical studies

“…The effect of pressure on the T C and MCE can be understood in terms of the pressure-tuned FM interaction. 86 It is well known that the conventional DE and also multiple DE interactions 40 depend on the lattice parameters through both the Mn–O–Mn angle θ and the Mn–O bond length d Mn–O , as well as the strength of the spin-lattice coupling in these manganites. T C is proportional to the e g -electron bandwidth T C = θW = β cos 2 θ /( d Mn–O ) 3.5 , where β is a constant.…”

Novel synthetic approach to the preparation of single-phase BixLa1−xMnO3+δ solid solutions

“…These materials offer new areas of applications, such as AC/DC magnetic field sensors, microwave resonators, and new data storage media [5,6]. LaMnO 3 perovskite is a material, which exhibits interesting magnetic, ferromagnetic, magnetocaloric, and electrical properties [7][8][9][10]. By substituting La 3+ with similar ionic radius and isovalent Bi 3+ , the multiferroic BiMnO 3 perovskite was obtained showing the possibility of coexistence of both ferromagnetism and ferroelectricity [11,12].…”