Physical properties of Al doped Ba hexagonal ferrite thin films

Abstract

We developed the thin film microwave magnetic material, M-type barium hexagonal ferrite (BaM) doped with Al, for signal processing devices operating above 40 GHz with little to no applied magnetic field. Al was chosen as the dopant material because it significantly increases the already strong anisotropy field of BaM. A series of thin film BaAlxFe12-xO19 samples, x ranging from 0 to 2 in 0.25 steps, were deposited on Pt templates using a metal-organic decomposition growth technique. The resulting films are polycrystalline and highly textured, with the hexagonal c-axis directed out of plane. These films are also self-biasing; easy axis hysteresis loops have a high squareness ratio, s, in the 0.83-0.92 range. As expected, the anisotropy field increases with x, ranging from 1.34 to 2.19 × 106 A/m (16.9-27.5 kOe) for x = 0-2, while the saturation magnetization Ms decreases with x, ranging from 0.334 to 0.175 × 106 A/m (4πMs = 4.2-2.2 kG) for x = 0-2. These values were measured at room temperature, but the temperature dependence of these quantities was also measured below room temperature, down to 30 K. The measured ferromagnetic resonance linewidths, on the order of 12-30 × 103 A/m (140–370 Oe) for compositions below x = 1, indicate device-quality films. Above a certain threshold, the linewidth increases linearly with frequency at a rate of 0.2-0.64 × 103 (A/m)/GHz (2.5-8 Oe/GHz) for x = 0–1, respectively. The behavior of the linewidth is correlated with the structural properties of the films measured using x-ray diffraction and atomic force microscopy. The results of magnetic force microscopy, Curie point measurements, spectral ellipsometry (index of refraction), and magneto-optical measurements are also included and discussed.

Curie temperature and magnetic properties of aluminum doped barium ferrite particles prepared by ball mill method

“…The measured temperature dependence of the saturation magnetization is also slightly different when our bulk samples are compared with thin films using SQUID magnetometer. 12 For our bulk samples, we observed a linear decrease of saturation is nearly equal for x=6 (see Figure 6). This result confirms earlier Mossbauer reports.…”

“…For small doping levels with Al (x<1), Tc is higher than that observed in thin films. 12 However, the rate of decrease of Tc is very similar. The measured temperature dependence of the saturation magnetization is also slightly different when our bulk samples are compared with thin films using SQUID magnetometer.…”

Structural and millimeter-wave characterization of flux grown Al substituted barium hexaferrite single crystals

“…Modification of barium hexaferrite (BaFe 12 O 19 ) by substitution of iron atoms gives significant changes in physical and chemical characteristics such as magnetocrystalline anisotropy, coercive force or Curie temperature [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. Hexagonal ferrites with large magnetocrystalline anisotropy are promising for mm-wave applications as well as for use in sub-terahertz range.…”

“…Among them are thin-film technologies such as liquid phase epitaxy [26], pulsed laser deposition [27,28], screen printing technique [29], and metal organic decomposition [4]. The main methods for nano-and micro-particle synthesis are chemical co-precipitation method [30], hydrothermal reaction [31], sol-gel process [32], solution combustion technique [2], ceramic method [33], mechano-thermal treatment [34], and reverse microemulsion technique [35].…”

Magnetic Properties of Poly (Divinylbenzene, Ethylene Glycol Dimethacrylate and Vinyl Alcohol) Containing Barium Ferrite Nanoparticles

“…Barium ferrite that has hexagonal crystal structure is a well known high performance permanent magnetic material and used in production as a disk driver, microwave device [8], and magnetic recording media [9] in recent years.…”