Structural, Dielectric, and Magneto‐Optical Properties of Al‐Cr Substituted M‐Type Barium Hexaferrite

Abstract

M‐type barium hexaferrite, BaFe12‐2xAlxCrxO19 (x = 0.0, 0.2, 0.4), is prepared using sol–gel auto‐combustion method and calcined at 1000 °C for 7 h. The effects of Al‐Cr substitution on the properties of the barium hexaferrite are investigated through XRD, FTIR, FESEM, UV‐vis‐NIR, VSM, and impedance analyzer. XRD analysis reveals the formation of hexaferrites with single phase and no impurity phase is detected. FTIR spectra show bands at 437 and 590 cm−1 which indicate the possible of hexaferrites. The micrographs of FESEM shows agglomerated grains with hexagonal plate‐like shape while the EDX spectra confirm the composition of the synthesized samples. Dielectric constant decreases abruptly at lower frequencies and an increment in dielectric constant at much higher frequency region is observed. Grain boundaries dominate the AC conductivity at lower frequencies while the grains could be responsible for the observed dispersion at higher frequencies. The values of coercivity for all the samples are found to be greater than 1200 Oe; this makes the prepared samples useful for high‐density perpendicular magnetic recording media.

Experimental and Theoretical Realization of Morphology and Frequency Tuned Charge Transport Dynamics in Co-Zn Doped SrM Hexaferrite: Electrical, Impedance and Relaxation Realm

“…2. 19 As the content of Co-Zn ions increases, a change in the intensity of peaks and shift in the Bragg angle is observed, as shown in Fig. 2.…”

Topical Review: Progress and Prospects of Hard Hexaferrites for Permanent Magnet Applications

“…Larger specific magnetizations were observed by Zn 2+ doping combined with other diamagnetic ions, Ti [140], Zr [141], Sn [142], Nb [144], V [144], Sb [144], La [145] or with paramagnetic Ni cations [139] that gives rise to ferrites with σ S between 75 and 110 A m 2 kg −1 . Also the double doping of BFO with diamagnetic Al 3+ and paramagnetic Cr 3+ cations [146] gives rise to a ferrite with a maximum specific magnetization of 88 A m 2 kg −1 for x = 0.4.…”

“…The enhancement of the magnetization has been observed also in other compositions. Trudel et al [146] investigated the double substitution of Al + and Cr 3+ cations in BaFe 12−2x Al x Cr x O 19 obtained by auto combustion sol-gel. For x = 0.4 the doped ferrite exhibits a specific magnetization of 88 A m 2 kg −1 , larger than the corresponding BFO (81 A m 2 kg −1 ) and similar mass density.…”

“…The ferrites with σ S < 100 A m 2 kg −1 (22)(23)(24) exhibit H c > 159 kA m −1 similar to those of standard hard hexaferrites. The only exception is the work of Trudel et al [146] in AlCr-BFO. For x = 0.4 the doped ferrite exhibits both a larger specific magnetization (88 A m 2 kg −1 ) and a coercive field (318 kA m −1 ) than the corresponding magnetization (81 A m 2 kg −1 ) and H C (127 kA m −1 ) of BFO.…”

“…Different doping approaches were investigated to improve the results obtained in Al doped hexaferrites [146,164,165,167,168] Trudel et al [146]. investigated the Cr doping of Al-SFO.…”