Structural and magnetic properties of La3+ ion doped Ni–Cu–Co nano ferrites prepared by sol–gel auto-combustion method

Abstract

Lanthanum doped Ni–Cu–Co nano ferrites with the chemical composition Ni0.2Cu0.1Co0.7Fe2−xLaxO4 (x = 0.0, 0.025, 0.05, 0.075, 0.1) were prepared by sol–gel auto-combustion technology. All samples were sintered at a temperature of 950 ℃. The X-ray diffraction (XRD) analysis verifies that all the samples of the formation of the cubic spinel structure. It turns out that with the addition of La3+ ions, the lattice constant decreases, and with the addition of La3+ ions, the lattice constant increases. The obtained Fourier transform infrared (FT-IR) measurement also confirms the formation of the spinel structure. With the increase in La, the higher frequency ν1 is slightly moving toward the high-frequency side. Transmission electron microscopy (TEM) images show the presence of particles, which are spherically cubic shaped crystallites. The presence of constituent’s, i.e., the presence of ingredients, namely, Ni, Cu, Co, Fe and La were authenticated by energy dispersive X-ray analysis (EDX). It was confirmed La3+-doping was successfully achieved. The magnetic parameters were measured by Vibrating sample magnetometer (VSM). The saturation magnetization, remanent magnetization, coercivity, anisotropy constant first increase and then decrease with the La content increases. The sample had the best magnetic properties when the doping content of La at x = 0.025. This indicates that appropriate doping can improve the magnetic properties of the samples. The reduction of the magnetic moment can be attributed to non-magnetic La3+ ions in place of Fe3+ ions (5µB), which results in a reduction of net total magnetic moment.