Site occupancy and anisotropy distribution of Al substituted Ba‐ferrite with high coercivity

Abstract

PACS 75.30.Gw, 75.50.Vv, 76.80.+y The site occupancy and anisotropy distribution of Al substituted BaFe 12-x Al x O 19 (0.0 ≤ x ≤ 4.0) have been studied with Mössbauer spectroscopy, X-ray diffraction, and vibrating sample magnetometry. The results suggest that the coercivity, magnetization, and magnetocrystalline anisotropies are closely related to the distributions of Al 3+ ions on the five iron sites. Mössbauer spectra indicated that Al 3+ ions have a strong preference for the 4f 1 , 2a and 12k sites. The substitution of Al 3+ by Fe 3+ in the system causes a drastic reduction of the saturation magnetization while the coercivity first increases to 8.6 kOe, for x = 2.0, and then decreases to 6.9 kOe, for x = 4.0. The origin of the changes in the magnetic properties caused by Al 3+ substitution can be attributed to the site preferences.

Mössbauer studies of La–Zn substitution effect in strontium ferrite nanoparticles

“…In this paper, we focused the effect of non-magnetic ions on the Mo¨ssbauer spectra [8] such as the Zn occupation of 4f 1 sites in the M-type hexagonal structure. Their magnetic and structural properties were characterized using the following measurements: an Xray diffractometry (XRD), a vibrating sample magnetometer (VSM), thermal analysis such as thermogravimetry analysis (TGA), and differential thermal analysis (DTA).…”

Preparation of Al3+-Co2+ co-substituted M-type SrCaNd hexaferrites and their controlled magnetic properties

“…43 The results of Mössbauer investigation of Al substituted M-type hexaferrites indicated that Al 3+ ions have a strong preference for 4f 2 , 2a and 12k sites. 44,45 Mössbauer investigation confirmed that Co 2+ ions substitute for Fe 3+ ions at 4f 2 (mainly) and 2a sites. 46 48 The Al 3+ ions are nonmagnetic while Co 2+ has a magnetic moment of 3.7µ B which is smaller than that of Fe 3+ (5 µ B ).…”

“…It is known that the high magnetocrystalline anisotropy constant of Mtype hexaferrites mainly stem from Fe 3+ ions at the 2b and 4f 1 . 50,51 It has been reported that Al 3+ ions have a strong preference for 4f 2 , 2a and 12k sites, 44,45 and Co 2+ ions substitute for Fe 3+ ions at 4f 2 (mainly) and 2a sites. 46,47 Therefore, according to the formula (6), the increase of intrinsic coercivity (H cj ) with increasing AlCo content (x) from 0.0 to 0.2 should be due to the increase of magnetocrystalline anisotropy constant.…”

Effects of La doping on the structural and magnetic properties of Sr1−xLaxFe11.75Co0.10Zn0.15O19 hexagonal ferrites

“…Rai et al 21 have prepared Ho 31 -doped barium hexaferrites BaFe 12À2x Ho 2x O 19 (0 # x # 1.0) and found that coercivity (H c ) shows a maximum value at x 5 0.4, and then a decreasing trend is observed in the values of coercivity (H c ) and saturation magnetization (r s ) with the increase of Ho content. Choi et al 22 have studied the magnetic properties of Al-substituted BaFe 12Àx Al x O 19 (0 # x # 4.0) and found that the substitution of Al 31 at the iron sites in the system causes a drastic reduction in saturation magnetization (r s ), while the coercivity (H c ) first increases to 684.7 kA/m, for x 5 2.0, and then decreases to 549.4 kA/m, for x 5 4.0. Yang and Liu 23 …”