Effects of Ga–Cr substitution on structural and magnetic properties of hexaferrite (BaFe12O19) synthesized by sol–gel auto-combustion route

I. Ali
Higher Education Department, Government of Punjab,
Pakistan

Keywords: hexaferrites, sol–gel auto-combustion, X-ray diffraction, magnetic measurements

Summary:

A series of single phase and nanostructured Cr–Ga substituted M-type hexaferrites BaCrxGaxFe12—2xO19 (x = 0.0–0.4) were synthesized by sol–gel auto-combustion route. The powder samples were pressed into pellets of diameter 12 mm using an excellent technique Cold Isostatic Pressing (CIP) at a pressure of 2000 bar for higher densification. The powdered samples were sintered at 1000 °C for 2 h and character- ized by different experimental techniques such as differential scanning calorimetry (DSC), thermogravi- metry (TG), Fourier transform infrared spectroscopy (FTIR), X-ray diffractions (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDXS) and vibrating sample magnetometry (VSM) magnetometry analyses. DSC–TG analysis was carried out to observe the transformation of different phases during heat treatment. X-ray diffraction (XRD) confirmed the formation of single phase M-type hexagonal ferrites. The crystallite size calculated by the Scherer equation was found to be in the range of 30–48 nm, which is small enough to obtain a suitable signal-to-noise ratio in the high density recording media. The saturation magnetization and retentivity were observed to increase from 2.78× 103 to 2.385 × 103 Gauss and 1.286 × 103 to 1.677 × 103 Gauss, respectively. The coercivity (iHc and bHc) enhanced which is attributed to increase in the magnetocrystalline anisotropy. The high val- ues of retentivity and coercivity make these materials best candidate for high density recording media and permanent magnets.