Barium Ferrite Samples Research Articles

Determination of angular dependence of the critical field of barium ferrite from remanence and microwave measurements (abstract)

The distribution of the critical field of nontextured polycrystalline ferrite is determined. Barium ferrite samples are saturated in one direction and measured with a field H applied at an angle θ to the saturation field. The measured quantities are the remanent magnetization and the microwave hysteresis including minor loops. Especially the microwave absorption curves allow direct analysis of the critical field as a function of the orientation angle ϑ0 between H and the easy axis. Starting with these data a fit of the calculated to the measured remanence curves yield the distribution. The figure shows the critical field distribution of a ferrite sample with large coercivity. Additionally the calculated and measured resonance fields ares are given. All field strengths are normalized to the anisotropy field, which can also be determined from the microwave measurement.1

Effective linewidth measurements at 36 GHz in hexagonal and cubic ferrites

Effective linewidth measurements at 36 GHz are reported for barium ferrite, several W-type single-crystal hexagonal ferrites, and for polycrystalline LiZn ferrite. In general, the effective linewidths for the W-type ferrites were relatively large—several hundred oersteds. Values of ΔHeff for the barium ferrite samples were tens of oersteds, similar to the ferromagnetic resonance (FMR) linewidths for these materials. The LiZn samples showed effective linewidths significantly below the FMR values. The results indicate that the two-magnon loss mechanism is the predominant factor in the polycrystalline LiZn, but contributes little to the ferromagnetic loss in single-crystal barium ferrite. The data for the W-type ferrites show that the intrinsic loss for these single-crystals is a significant part of the ferromagnetic resonance linewidth.

Mössbauer measurements of the bipyramidal lattice site in BaFe 12O 19

Mössbauer measurements have been made on polycrystalline barium ferrite samples. The subspectrum corresponding to the iron ion in the bipyramidal lattice site in the temperature range from T = 4.2K up to T = 870K was obtained. Based on the temperature dependence of the unusually large quadrupole splitting due to ferric iron in the bipyramidal position, a model of this lattice site is proposed in which the iron ion is located at one of two equivalent positions of Wyckhoff notation 4 e, separated by a potential barrier. At sufficiently high temperature the ion jumps between the two 4 e sites with a jump frequency which is greater than the inverse of the lifetime of the 14.4 keV state of 57Fe. This is in agreement with Mössbauer measurements, molecular-orbital studies and previous X-ray data.

The Problem of Texture in Mössbauer Spectroscopy

In Mössbauer spectroscopy it is desirable to work with single crystals or with polycrystalline material of random orientation. The actual, most occuring, case of preferred orientation (texture) and its influence on the relative line intensities of hyperfine split Mössbauer spectra is analysed. Texture information which can be obtained from such an analysis is demonstrated with variously prepared barium ferrite (Ba Fe12 O19) samples.