The composition dependence of field induced anisotropy KU of field annealed soft ferromagnetic (Co1−xFex)89Zr7B4 and (Co1−xFex)88Zr7B4Cu1 amorphous and amorphous/nanocrystalline “nanocomposite” melt spun ribbons is investigated. With the exception of the highest Co-containing alloys (x<∼0.10), the observations are discussed in terms of a superposition of directional pair ordering of Fe,Co atoms and an additional contribution presumably due to the presence of Zr and B in both the field crystallized and field annealed amorphous ribbons. The highest Co-containing alloys (x<∼0.10) contain multiple nanocrystalline phases (bcc, fcc, and hcp) for which a peak in KU is observed (KU∼2000–2500 J/m3). In this framework, asymmetry in the compositional dependence of KU resulting in larger values for Co-rich alloys relative to Fe-rich alloys for both the field crystallized and field annealed amorphous alloys is explained in terms of a strong dependence of the Curie temperature of the amorphous phase on the Co content.

A new high-saturation induction, high-temperature nanocomposite alloy for high-power inductors is discussed. This material has FeCo with an A2 or B2 structure embedded in an amorphous matrix. An alloy of composition Fe56Co24Nb4B13Si2Cu1 was cast into a 1.10in. wide, 0.001in. thick ribbon from which a toroidal core of approximately 4.25in. outer diameter, 1.38in. inner diameter, and 1.10in. tall was wound. The core was given a 2T transverse magnetic field anneal, and impregnated for strength. Field annealing resulted in a linear B-H response with a relative permeability of 1400 that remained constant up to field strengths of 1.2T. The core was used to construct a 25μH inductor for a 25kW dc-dc converter. The inductor was rated for operation in discontinuous conduction mode at a peak current of 300A and a switching frequency of up to 20kHz. Compared to commercially available materials, this new alloy can operate at higher flux densities and higher temperatures, thus reducing the overall size of the inductor.

A stable Fe 23 B 6-type phase formed in a nanocomposite soft magnetic alloy Fe 40 Co 40 Nb 4 B 13 Ge 2 Cu 1 after thermal treatment was investigated. The primary crystallization temperature and second crystallization temperature for this alloy were determined to be 405 and 740°C, respectively. After annealing the sample at 820°C for 1 h, a Fe 23 B 6-type phase ͑FeCoNb͒ 23 B 6 was observed. The structural information was investigated by x-ray diffraction, transmission electron microscopy, and three-dimensional atom probe. The Fe 23 B 6-type phase contains about 33± 5 at. % Fe, 38± 5 at. % Co, 7 ± 1 at. % Nb, and 20± 3 at. % B. The Nb atoms tend to occupy the 8c sites and Co/ Fe atoms occupy the 4a, 32f, and 48h sites of the Fm3m space group for this structure.

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Ferromagnetic resonance(FMR) study on sputtered Ni 80 Fe 20 with various thickness from 2 nm to 38.5 nm sandwiched by Ta has been made systematically with different dc magnetic field orientations. The FMR spectra were analyzed and fitted theoretically with Laudau-Lifshitz-Gilbert equation. The variations of magnetization, magnetic anisotropy up to fourth-order term with thickness of samples were obtained. The analysis of the FMR peak-to-peak linewidth was made by the homogenous and inhomogeous contributions, and the damping constants of samples were calculated. The experimental data were fitted by theoretical model and there were some abnormal changes in the magnetic parameters with the sample thickness.