Schottky-like anomaly in the heat capacity and magnetocaloric effect of charge-ordered single-crystalline (Sm, Ca, Sr)MnO3 compound

Abstract

Abstract We present a comprehensive experimental study on the magnetic and magnetocaloric properties of a charge-ordered single-crystalline Sm0.5Ca0.25Sr0.25MnO 3 compound. The studies on x-ray photoelectron spectroscopy (XPS) reveals the presence of an equal distribution of Mn 3 + and Mn 4 + ions in the studied system. The Oxygen, O1s-core level spectra have been simulated with three binding energies curves, which correspond to the O 2 − ions, O 1 − ions, and chemically adsorbed oxygens, O c h e m . The XPS analysis of the O1s-core-level spectra and magnetic characterizations indicate the proper stoichiometry of the present sample. Considering the change of volume phase fraction in the isofield magnetization measurements during the first-order magnetic phase transition from paramagnetic state to ferromagnetic state, the isothermal magnetic entropy change ( Δ S) has been estimated based on the modified Clausius–Clapeyron equation. An inverse magnetocaloric effect has also been noticed in the - Δ S vs. T plot calculated by Maxwell’s thermodynamic relation, suggesting the dominant antiferromagnetic ground state supported by a charge-ordered phase of the studied system. The high-temperature zero-field heat capacity (C P ) data can be well-interpreted quantitatively using the Debye model of heat capacity. With the extracted magnetic heat capacity (C m a g ) data, the temperature variation of the magnetic entropy (S(0)), as well as the adiabatic temperature change ( Δ T a d ), have been estimated. In addition to that, the low-temperature C P data displays a Schottky-like anomaly in the temperature region between 2 K and 20 K. The experimental data points are successfully fitted by considering the various contributing factors of the low-temperature heat capacity such as the lattice-phonon vibration (C l a t ), antiferromagnetic spin-wave (C m a g ), and the two-level Schottky function (C s c h ) due to the energy splitting of the Sm 3 + cations.