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ORIGINAL PAPER

Microstructural Analysis, Magnetic Properties, and Critical Behavior of La0.7Ba0.15Sr0.15CoO3 Perovskite Bandar Alzahrani 1 & Gönül Akça 2 & Sobhi Hcini 3 & Mohmed Lamjed Bouazizi 1 Received: 19 August 2020 / Accepted: 25 September 2020 # Springer Science+Business Media, LLC, part of Springer Nature 2020

Abstract We have reported the sol-gel synthesis and microstructural, magnetic, magnetocaloric, and critical behaviors of La0.7Ba0.15Sr0.15CoO3 cobaltite. The XRD data refined by Rietveld technology confirms that a sample has a pure perovskite phase with rhombohedral structure. We tested the magnetization curve near the phase transition temperature (TC) from ferromagnetic (FM) to paramagnetic (PM), and made the Arrott diagram which confirmed the existence of the secondary phase transition. The obtained magnetic constants from hysteresis loop offer to the sample the possible use in some interesting technological applications. The M(μ0H, T) isothermal magnetizations have been analyzed to estimate the critical exponents (β, γ, and δ). We found that β exponent is close to that of the mean-field model; however, γ and δ exponents belong to an unconventional model. The reliability of the estimated critical exponents was checked from the magnetic field variations of the magnetic entropy change (− ΔSm) and the relative cooling power (RCP). Keywords Cobaltites . Microstructural study . Magnetic behavior . Critical exponents

1 Introduction For several years, numerous studies have been conducted on perovskite oxides in order to obtain suitable materials for technological applications such as magnetic memory devices, solid oxide fuel cells, gas separation membranes, magnetic refrigeration, biology, accumulators, chemical reactors, and many other applications [1–5]. Among perovskite families, the cobaltite oxides with the general formula of R1-xAxCoO3 (R = trivalent rare earth elements, A = divalent alkaline elements) have a great wealth of physical properties. These

* Sobhi Hcini [email protected] * Mohmed Lamjed Bouazizi [email protected] 1

Department of Mechanical Engineering, College of Engineering, Prince Sattam Bin Abdulaziz University, Al Kharj 11942, Saudi Arabia

2

Faculty of Sciences and Letters, Department of Physics, Çukurova University, 01330 Adana, Turkey

3

Faculty of Science and Technology of Sidi Bouzid, Research Unit of Valorization and Optimization of Exploitation of Resources, University of Kairouan, 9100 Sidi Bouzid, Tunisia

materials are distinguished from the rest of the perovskite materials by a unique characteristic due to the presence of Co3+ and Co4+ ions which introduces an additional degree of freedom associated with the nature of their spin states [6]. Three different spin-state configurations for Co3+ and Co4+ ions can be presented for cobaltites: low spin (LS, t 62g e0g ), intermediate spin (IS, t 52g e1g ), or high spin (HS, t 42g e2g ) states based on crystal structure, temperature, and doping content [7]. This brings on variances in the physical and magnetic prop