Microstructural analysis, magnetic properties, magnetocaloric effect, and critical behaviors of Ni0.6Cd0.2Cu0.2Fe2O4 ferrites prepared using the sol-gel method under different sintering temperatures

Noura Kouki; Sobhi Hcini; Michel Boudard; Reema Aldawas; Abdessalem Dhahri

doi:10.1039/c8ra09113g

Microstructural analysis, magnetic properties, magnetocaloric effect, and critical behaviors of Ni_0.6Cd_0.2Cu_0.2Fe₂O₄ ferrites prepared using the sol-gel method under different sintering temperatures

RSC Adv. 2019 Jan 15;9(4):1990-2001. doi: 10.1039/c8ra09113g. eCollection 2019 Jan 14.

Authors

Noura Kouki^{1

2}, Sobhi Hcini³, Michel Boudard⁴, Reema Aldawas¹, Abdessalem Dhahri⁵

Affiliations

¹ Department of Chemistry, College of Science and Arts, Qassim University Buraydah Saudi Arabia.
² Laboratory of Water, Membranes and Environment Biotechnology (EMBE), Technopole of Borj Cedria (CERTE) 2050 Hammam Lif Tunisia.
³ Faculty of Science and Technology of Sidi Bouzid, Research Unit of Valorization and Optimization of Exploitation of Resources, University Campus Agricultural City, University of Kairouan 9100 Sidi Bouzid Tunisia hcini_sobhi@yahoo.fr.
⁴ LMGP, University of Grenoble Aples, CNRS 38000 Grenoble France.
⁵ Department of Physics, Laboratory of Physical Chemistry of Materials, Faculty of Science of Monastir, University of Monastir 5019 Monastir Tunisia.

Abstract

This work focuses on the microstructural analysis, magnetic properties, magnetocaloric effect, and critical exponents of Ni_0.6Cd_0.2Cu_0.2Fe₂O₄ ferrites. These samples, denoted as S1000 and S1200, were prepared using the sol-gel method and sintered separately at 1000 °C and 1200 °C, respectively. XRD patterns confirmed the formation of cubic spinel structures and the Rietveld method was used to estimate the different structural parameters. The higher sintering temperature led to an increased lattice constant (a), crystallite size (D), magnetization (M), Curie temperature (T _C), and magnetic entropy change (-ΔS _M) for samples that exhibited second-order ferromagnetic-paramagnetic (FM-PM) phase transitions. The magnetic entropy changed at an applied magnetic field (μ ₀ H) of 5 T, reaching maximum values of about 1.57-2.12 J kg^-1 K^-1, corresponding to relative cooling powers (RCPs) of 115 and 125 J kg^-1 for S1000 and S1200, respectively. Critical exponents (β, γ, and δ) for samples around their T _C values were studied by analyzing the M(μ ₀ H, T) isothermal magnetizations using different techniques and checked by analyzing the -ΔS _M vs. μ ₀ H curves. The estimated values of β and γ exponents (using the Kouvel-Fisher method) and δ exponent (from M(T _C, μ ₀ H) critical isotherms) were β = 0.443 ± 0.003, γ = 1.032 ± 0.001, and δ = 3.311 ± 0.006 for S1000, and β = 0.403 ± 0.008, γ = 1.073 ± 0.016, and δ = 3.650 ± 0.005 for S1200. Obviously, these critical exponents were affected by an increased sintering temperature and their values were different to those predicted by standard theoretical models.