Effect of Co ²⁺ substitution on the structural, terahertz and magnetic characterization of NiZn ferrites

Abstract

Abstract We present detailed studies on spinel structured Ni 0.5 Co x Zn 0.5− x Fe 2 O 4 ( x = 0.1, 0.2 and 0.3), synthesized by sol–gel combustion method. In addition to the structural properties, we present optical dielectric and magnetic response of this system as a function of x . From x-ray diffraction analysis, a single-phase formation in cubic spinel structure was confirmed with an average crystallite size ( D avg ) variation of 46–61 nm. X-ray diffractograms were analyzed to evaluate the lattice constant ( a ), x-ray density ( ρ x ) and porosity ( P ) in percentage. Energy dispersive x-ray spectroscopy was used to delimit the compositional mass ratios. Terahertz (THz) time-domain spectroscopy measurements were performed to investigate the refractive index ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mover> <mml:mi>n</mml:mi> <mml:mo stretchy="false">ˆ</mml:mo> </mml:mover> <mml:mrow> <mml:mtext>s</mml:mtext> </mml:mrow> </mml:msub> </mml:math> ) of the samples at room temperature in a frequency range from 0.2 to 2.5 THz. Real and imaginary components of complex optical dielectric constant ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mover> <mml:mi>ε</mml:mi> <mml:mo stretchy="false">ˆ</mml:mo> </mml:mover> </mml:mrow> <mml:mrow> <mml:mtext>s</mml:mtext> </mml:mrow> </mml:msub> </mml:math> ) with the increase of Co 2+ content were deduced using THz spectroscopy data. The complex optical dielectric constant for the substitution of Co 2+ content at x = 0.1, 0.2 and 0.3, was determined within 5% error ∼9.6 + i0.07, ∼10.9 + i0.2 and ∼11.7 + i0.5, respectively. The magnetic measurements were performed at a temperature range of 300–50 K using a superconducting quantum interference device vibrating sample magnetometer under an applied magnetic field of ±5 tesla. We found the highest saturation magnetization ( M s ) of about 86.7 emu g −1 , 83.5 emu g −1 and 80.4 emu g −1 for the substitution of Co 2+ content at x = 0.1, 0.2 and 0.3, respectively at room temperature.

Topics & Concepts