Fulin Wei

The effects of La–Zn substitution on the magnetic properties of Sr-magnetoplumbite ferrite nano-particles

The La-Zn substituted Sr-Magnetoplumbite ferrite LaxSr1-xZnxFe12-xO19 (x = 0 0.6) fine particles were prepared to investigate the effects of the substitution on the magnetic properties of the samples. It is observed, with increasing substitution rate, that the saturation magnetization M-s as well as the magnetocrystalline anisotropy constant K-U1 increased up to a maximum for about x = 0.3, then decreased rapidly. The value of dH(c)/dT also reduced rapidly from about 5.5 Oe K-1 (for x = 0) to - 0.5 Oe K-1 (for x = 0.4). A qualitative explanation was given with respect to the hypothesis of crystalline electronic field and the single ion model

Structure and magnetic properties of Zn–Ti-substituted Ba-ferrite particles for magnetic recording

Abstract The formation process of Zn–Ti-doped Ba-ferrite particles was investigated by the X-ray diffraction technique, transmission electron microscope and magnetic measurements. The effects of heating temperature T h and the Zn–Ti substitution x on the microstructure and magnetic properties of BaFe 12−2 x Zn x Ti x O 19 particles with x =0.10–0.80 were studied. The temperature dependence of magnetic properties of these particles was measured.

Magnetic properties of BaFe12−2xZnxZrxO19 particles

ZnZr doped barium ferrite single domain particles BaFe12−2xZnxZrxO19 with 0⩽x⩽0.8 were prepared by the chemical coprecipitation method. With increasing doping concentration x, the magnetocrystalline anisotropy and thus the coercivity was drastically decreased. This was mainly due to the substitution of Fe3+ ions in the magnetoplumbite structure and strongly affected by the selective occupation of nonmagnetic cations on sublattice sites. Compared with coercivity, the zero-field saturation magnetization decreased much slower. The particle size decreased with x, while both of the lattice parameters “a” and “c” increased. The high-field differential susceptibility showed an increase with increasing doping concentration x, revealing the breakdown of the magnetic collinear structure and subsequently increased fraction of surface canted spins.

Frequency multiplying behavior in a magnetoelectric unimorph

We observe frequency multiplying behavior in a magnetoelectric (ME) unimorph: such a frequency-multiplied signal is generated when the input frequency (fin) of an alternating current magnetic field (Hac) is around 1/n (n denotes integer) of the mechanical resonance frequency (fr) of the device. We observe both odd and even harmonic signals when a direct current magnetic field (Hdc) is applied, whereas only even harmonic signals arise for Hdc = 0. This behavior results from the combined effect of the nonlinear character of the Metglas magnetostriction and a mechanical resonance phenomenon in the magnetoelectric unimorph.

La–Zn substituted hexagonal Sr ferrite thin films for high density magnetic recording

La–Zn substituted M type Sr-ferrite thin films were prepared by conventional rf diode sputtering. The crystallography, surface morphology, magnetic properties, and their temperature dependence were investigated by x-ray diffractometry, atomic force microscopy, and vibrating sample magnetometry. La–Zn substitution reduces the grain growth rate, so that it was possible to obtain fine grains with mean grain size about 12 nm×12 nm. Suitable amount of La–Zn substitution increases the saturation magnetization Ms of the films without changing the magnetocrystalline anisotropy of the material. As a result, the coercivity Hc increases with the increase of the La–Zn substitution. La–Zn substitution also reduces the values of dHc/dT of the films in the vicinity of room temperature.

The temperature dependence of magnetic properties of Zn–Ti substituted Ba-ferrite particles for magnetic recording

Abstract It was shown that the morphological and magnetic properties of Zn–Ti doped Ba-ferrite particles are suitable for magnetic recording. In order to clarify the temperature dependence of the magnetic properties of these particles, BaFe10.8−2xZnxTixO19 particles with the nominal composition x=0.0–0.50 were prepared by synthesis from salt melts. The saturation magnetization Ms, magnetic anisotropy field HA and magnetocrystalline anisotropy constant K1 of the above-mentioned particle assemblies were estimated by using the law of approach to saturation of polycrystalline ferrite, and the Curie temperature Tc was determined by the thermodynamic relation. With an increasing x, the Tc decreased, while the lattice parameters a, c and M s have an unnoticeable maximum at x=0.20. The Hc(T) curves of samples with different x show that all particles have positive temperature coefficient in the vicinity of room temperature, which decreases with increasing x. The Ms(T), H A (T) and K 1 (T) were determined and discussed.

A study of sputtering process for nanocrystalline FeAlN soft magnetic thin films

Abstract Nanocrystalline FeAlN thin films were successfully prepared by three ways: the growth of deposited nanocrystalline film by ex-situ process, in-situ process and controlling crystallization of deposited amorphous films. The magnetic properties and microstructure such as aspect and surface morphology were investigated. It is found that the FeAlN films by ex-situ process show the best soft magnetic properties: higher saturation and lower coercivity. The FeAlN films synthesized by controlling the crystallization of as-deposited amorphous films exhibit the highest thermal stability.

Magnetic and crystallographic properties of La–Zn substituted Sr-ferrite thin films

La–Zn substituted Sr-ferrite thin films were prepared by rf diode sputtering. The magnetic and crystallographic properties of the films were investigated by vibrating sample magnetometry and x-ray diffractometry. It is found that the texture of the films sensitively depends on the amount of substitution. Both the saturation magnetization Ms and coercivity Hc increase with the increase of La–Zn substitution. The increase of Hc is caused, in part, by the increase of K1 due to the substitution.

High frequency characteristics of FeCoAlO thin films combined the effects of stress and magnetic field

The soft magnetic FeCoAlO thin films with different response at high frequency were prepared by using RF magnetron sputtering. Two different configurations of the sputtering targets were used: the Al2O3 chips were placed on Fe70Co30 disk either uniformly dispersed on the sputtering area (Target-A) or dispersed on the half side of the sputtering area (Target-B). It was found that, although, the films deposited from both of Target A and B possessed good soft magnetic properties and in-plane uniaxial magnetic anisotropy, they showed different behaviors at high frequency. The films deposited by using Target-A have mean permeability of 500 and a cut-off frequency (fr) of around 780 MHz, while the films deposited by using Target-B have mean permeability of 200 and a fr of 3.4 GHz. The higher fr of the later corresponds to the higher uniaxial anisotropic field in the films deposited by using the Target-B, which due to an extra anisotropy induced by the stress resulted from gradient of the Al-O composition. By ad...

Effect of CrW underlayer on structural and magnetic properties of FePt thin films

L10 ordered FePt thin films with face-centered-tetragonal (001) texture have been prepared by magnetron sputtering on Cr100−xWx underlayer. The dependence of Cr100−xWx microstructure and FePt texture on the W content in the Cr underlayer was investigated. The addition of W element in Cr underlayer enhances the Cr (200) texture and increases the lattice constant of Cr, which is favorable for lowering the transformation temperature from fcc to fct phase because of the increase of the tensile stress along the FePt a axis. A good FePt (001) texture is obtained on the Cr85W15 underlayer with a substrate temperature of 400°C. The coercivity of FePt thin films on CrW underlayer is higher than on Cr underlayer and increases with increasing W content in the Cr underlayer because the formation of the CrW alloy inhibits the diffusion between FePt and CrW layer. A 5nm Pt intermediate layer was employed to suppress the diffusion between FePt and CrW underlayer further.