Structural and magnetic properties of Gd–Zn substituted M-type Ba–Sr hexaferrites by sol-gel auto-combustion method

Abstract

This work is report on Gd–Zn substituted M-type Ba–Sr hexaferrites with Ba0.5Sr0.5-xGdxFe12.0-xZnxO19 (0.0 ≤ x ≤ 0.4) by sol-gel auto-combustion method. X-ray diffractometer (XRD), Fourier transformer infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), X-ray Photoelectron Spectroscopy (XPS) and Quantum Design measurement system (SQUID) were used to characterize M-type Ba–Sr hexaferrites. The results of X-ray patterns showed that the single M-type hexaferrite phase can be obtained when x = 0.00–0.20, however the impurity phase (α-Fe2O3) was observed for the hexaferrites with Gd–Zn content (x) ≥ 0.30. FT-IR frequency bands in the range (581–592) cm−1 and (431–442) cm−1 corresponded to the formation of tetrahedral and octahedral clusters of metal oxides in the hexaferrites, respectively. XPS survey showed that hexagonal crystal structure was formed completely, which was correlated closely with the results of XRD patterns and FT-IR spectra. SEM revealed the shape of the hexagonal plate. Measurements of the magnetization versus the field M(H) of Ba0.5Sr0.5-xGdxFe12.0-xZnxO19 (0.0 ≤ x ≤ 0.4) hexaferrites were conducted at 5 and 300 K. Zero field cooling (ZFC) and field cooled (FC) measurement data did not show blocking temperature peak, indicating the ferrimagnetic behavior of prepared hexaferrites. Moreover, at low temperatures a spin glass behavior was observed. The squareness ratio (Mr/Ms) indicated the uniaxial anisotropy for various hexaferrites. The deduced values of saturation magnetization (Ms), the magneton number (nB) and the effective magnetic anisotropy constant (Keff) decreased, whereas the values of the anisotropy fields (Ha) and the coercive field (Hc) increased with increasing Gd–Zn content at both 5 and 300 K.