Benha University

Mohamed Ibrahim Mohamed Emam

Lecturer

Faculty of Engineering, Shoubra Mechanical Engineering

THE STUDY OF TEMPERATURE-DEPENDENT MAGNETIC PROPERTIES VARIATION IN CoCr2O4 NANOPARTICLES WITH (y = 0.8) AND WITHOUT COATING CONCENTRATION OF NON-MAGNETIC (SiO2)y

acta mechanica et automatica, • 2024
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Publication Information
Authors Ghazanfar MEHBOOB, Kashif NADEEM, Amjad IQBAL, Gohar MEHBOOB, Shahnawaz HUSSAIN, Mohamed RAGAB, Mazhar IQBAL, Sohaib AJMAL, Adel EL-MARGHANY
Keywords Not Available
Journal acta mechanica et automatica,
Publisher Sciendo
Volume 17
Issue Not Available
Pages Not Available
publication.type International
Paper Link Open Link
Supplementary Materials Not Available
Abstract
The present study investigates the temperature-dependent magnetic (MT) properties of CoCr2O4/(SiO2)y (y  0 and 0.8) nanoparticles. Nanoparticles were synthesised by using the conventional sol–gel technique. The X-ray diffraction (XRD) method confirmed the normal spinel structure of CoCr2O4 nanoparticles. The main peak analysis of the XRD pattern using Debye–Scherrer’s formula probes the mean crystallite sizes for coated and uncoated nanoparticles, and the sizes based on which the probes have been carried out amount to 19 nm and 28 nm, respectively. The transmission electron microscopy (TEM) image showed the non-spherical shape of these nanoparticles. Field-cooled (FC) and zero field-cooled (ZFC) MT plots were taken by using a superconducting quantum interference device (SQUID) magnetometer. Pure CoCr2O4 nanoparticles showed the ferrimagnetic transition at Curie temperature (Tc  99 K) on an applied field (H) of 50 Oe. Tc decreased up to 95 K with the increase in 80% SiO2 concentration in CoCr2O4 nanoparticles. For pure samples, conical spiral temperature (TS) and lock-in transition temperature (TL) remain unchanged with increasing magnetic field because of strong spin–lattice coupling. However, for 80% SiO2 impurity, the decrease in Tc was attributed to the reduction in surface disorder with a minor decline in TS and TL. The Ms declined with a decrease in temperature because of the existence of stiffed/strong conical spin-spiral and lock-in states in pure CoCr2O4 nanoparticles, while nanoparticles with 80% coating SiO2 concentration showed abnormal behavior. The coercivity increases with a decrease in temperature due to a decrease in thermal fluctuations at low temperatures for both samples. The fitting of coercivity (Hc) versus temperature plot by using Kneller’s law has given the values of coercivity constant (α) and coercivity at average blocking temperature (TB) for both samples, which are α  0.54, TB  75 K and α  1.59, TB  81 K, respectively. Hence, the increase in the concentration of SiO2 decreased nanoparticles size and surface disorder in CoCr2O4 nanoparticles while enhancing Ms below spin-spiral state ordering.
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