The magnetic properties of Fe‐Si‐B‐M (M: additives) alloys prepared by annealing amorphous alloys made by the single roller method over their crystallization temperature have been investigated for development of new Fe‐based soft magnetic alloys. Excellent soft magnetic properties were obtained by adding the two elements Cu and Nb to Fe‐Si‐B alloys. It was found that these new alloys, called ‘‘FINEMET,’’ have an ultrafine grain structure composed of bcc Fe solid solution. They are suitable for many kinds of magnetic components such as saturable reactors, choke coils, and transformers, because they have superior soft magnetic properties and a high saturation flux density, and because different types of B‐H hysteresis loops are obtained by magnetic field annealing.

New Fe-based soft magnetic alloys composed of ultrafine grain structure

We review work on In2O3:Sn films prepared by reactive e‐beam evaporation of In2O3 with up to 9 mol % SnO2 onto heated glass. These films have excellent spectrally selective properties when the deposition rate is ∼0.2 nm/s, the substrate temperature is ≳150 °C, and the oxygen pressure is ∼5×10−4 Torr. Optimized coatings have crystallite dimensions ≳50 nm and a C‐type rare‐earth oxide structure. We cover electromagnetic properties as recorded by spectrophotometry in the 0.2–50‐μm range, by X‐band microwave reflectance, and by dc electrical measurements. Hall‐effect data are included. An increase of the Sn content is shown to have several important effects: the semiconductor band gap is shifted towards the ultraviolet, the luminous transmittance remains high, the infrared reflectance increases to a high value beyond a certain wavelength which shifts towards the visible, phonon‐induced infrared absorption bands vanish, the microwave reflectance goes up, and the dc resisitivity drops to ∼2×10−4 Ω cm. The corre...

Evaporated Sn‐doped In2O3 films: Basic optical properties and applications to energy‐efficient windows

https://www.andrew.cmu.edu/user/dl0p/laughlin/pdf/PMS.pdf

Amorphous and nanocrystalline materials for applications as soft magnets

Weak localization in thin films: a time-of-flight experiment with conduction electrons

We report a study of the oxidation of TiN. In previous work, the oxidation kinetics for 350–450 °C were reported and an initiation time prior to fast oxidation was identified. In this study, x‐ray photoelectron spectroscopy was used to investigate the oxidation mechanisms at 350 °C during this initiation time period. The oxide thickness increases slowly with oxidation time and the film appears to change from an amorphous TiO2 layer to a crystalline TiO2 layer. Spectral features which are intermediate between TiO2 and TiN are reported and a model involving grain boundary oxidation is proposed. One of the thicker oxides studied was annealed in vacuum to 700 °C. Following oxidation, some of the capping oxide and much of the intermediate material is no longer in the analysis volume and we suggest that the oxygen and nitrogen is being dissolved into the bulk in much the same way that nonevaporable getters are activated before use.

Titanium nitride oxidation chemistry: An x‐ray photoelectron spectroscopy study

The magnetic ripple of thin films with uniaxial anisotropy is calculated for the field and the magnetization lying along the easy and the hard direction of the uniaxial anisotropy. For small dispersion of the direction of magnetization, the variational principle, applied to all energy terms including the exchange, crystalline anisotropy, uniaxial anisotropy, magnetostriction, magnetostatic, and stray field energies, yields a Bessel's differential equation. Its solutions (cylindrical functions) describe the two‐dimensional magnetic ripple of the film. Along the mean direction of the magnetization the fluctuations of the magnetization vector are much greater than perpendicular to it. In the first case these fluctuations are coupled by exchange forces, and in the second case by the stray field. The dispersion of the magnetization depends on the dispersion of the anisotropy, on the magnetic constants of the film, on the thickness of the film, and on the applied field. The theory is able to explain the image o...

Quantitative Calculation of the Magnetic Ripple of Uniaxial Thin Permalloy Films

A review is given about the assumptions the development, and the results of the ripple theory. The limits of the linear theory are pointed out. The result of this theory shows a very strong coupling of the magnetization dispersion perpendicular to the mean magnetization, which is caused by the internal demagnetizing field. The exchange constant of this magnetostatic coupling exceeds the quantum mechanical exchange constant A by orders of magnitude. The nonlinear ripple theory includes the component of the internal demagnetizing field parallel to the mean magnetization. This field becomes important when the rms values of the magnetization dispersion are \gapprox 2\deg . The nonlinear theory explains all deviations from a single domain behavior without introducing any special model.

Theory of magnetization ripple

Magnetic vortices play an important role in the switching behavior of micron- and submicron-sized ferromagnetic elements. We have prepared submicron permalloy elements by a combination of electron-beam lithography and liftoff technique on electron transparent membrane substrates. The magnetization reversal mechanism and the remanent magnetization configuration were observed by means of Lorentz transmission electron microscopy. In remanence, the investigated structures form a vortex configuration. In situ magnetizing experiments showed the possibility of adjusting the sense of magnetization rotation by introducing a slight geometric asymmetry to the otherwise circular nanostructures.

Magnetic switching of single vortex permalloy elements

Grain boundaries are known to reduce significantly the electrical dc conductivity of polycrystalline metallic materials. In this paper, we give a quantum mechanical calculation of the grain-boundary resistance based on the transfer-matrix approach. The results show an exponential decrease of the conductivity with respect to the number of grain boundaries per mean free path in accord with an empirical model proposed recently.

/pdf/grain-boundary-resistance-in-polycrystalline-metals-3a68hy1b7l.pdf

Grain-boundary resistance in polycrystalline metals.

Circular permalloy elements were fabricated by a combination of electron beam lithography, thermal evaporation and liftoff technique on electron transparent membrane substrates. The magnetic properties have been studied by Lorentz transmission electron microscopy. In situ magnetizing experiments have been carried out to obtain information about the nucleation and propagation of magnetic domains within the permalloy nanodisks and to determine the nucleation and saturation fields. The diameter of the patterned elements has been varied between 180 and 950 nm, the height was 15 nm. The experiments showed that the vortex configuration is the most favorable state in zero field conditions of all investigated permalloy nanodisks.

Horst Hoffmann

Papers

Quantitative Calculation of the Magnetic Ripple of Uniaxial Thin Permalloy Films

Theory of magnetization ripple

Magnetic switching of single vortex permalloy elements

Grain-boundary resistance in polycrystalline metals.

Lorentz microscopy of circular ferromagnetic permalloy nanodisks