Estimation of Energy Losses in Nanocrystalline FINEMET Alloys Working at High Frequency

Soft magnetic materials are at the core of electromagnetic devices. Planar transformers are essential pieces of equipment working at high frequency. Usually, their magnetic core is made of various types of ferrites or iron-based alloys. An upcoming alternative might be the replacement the ferrites with FINEMET-type alloys, of nominal composition of Fe73.5Si13.5B9Cu3Nb1 (at. %). FINEMET is a nanocrystalline material exhibiting excellent magnetic properties at high frequencies, a soft magnetic alloy that has been in the focus of interest in the last years thanks to its high saturation magnetization, high permeability, and low core loss. Here, we present and discuss the measured and modelled properties of this material. Owing to the limits of the experimental set-up, an estimate of the total magnetic losses within this magnetic material is made, for values greater than the measurement limits of the magnetic flux density and frequency, with reasonable results for potential applications of FINMET-type alloys and thin films in high frequency planar transformer cores.

Study on nanocrystalline grain size and quantitative change in Fe–Cu–Mo–Si–B soft magnetic alloy

In this paper, we studied the grain size and volume fraction change of [Formula: see text]-Fe(Si) nanocrystalline phase as a function of Cu, Mo and Si content in Fe[Formula: see text]Cu[Formula: see text]Mo3Si[Formula: see text]B9, Fe[Formula: see text]Cu1Mo[Formula: see text]Si[Formula: see text]B9, Fe[Formula: see text]Cu1Mo3Si[Formula: see text]B[Formula: see text], and also the annealing temperature and time in Fe[Formula: see text]Cu1Mo3Si[Formula: see text]B9 alloy. Cu is an element promoting ultrafine structure and crystallization progresses, it causes the grain size of the [Formula: see text]-Fe(Si) phase to decrease suddenly, the volume fraction of [Formula: see text]-Fe(Si) phase to increase only by adding 0.5 at.% Cu. Also, Mo causes the grain size of [Formula: see text]-Fe(Si) phase to decrease like Cu, while suppressing the increase of the volume fraction of [Formula: see text]-Fe(Si) phase, Si has no little effect on the grain size of [Formula: see text]-Fe(Si) phase, diffuses into the inner part of [Formula: see text]-Fe(Si) phase upto Si 13.5 at.%, but suddenly increases grain size above Si 13.5 at.%. The microstructure of Fe[Formula: see text]Cu1Mo3Si[Formula: see text]B9 alloy is nearly completed at 520[Formula: see text]C for about 20 min, the grain size is approximately 13.8–14.1 nm, the volume fraction of [Formula: see text]-Fe(Si) phase is within 61–66%, initial permeability at 1 kHz is within 59,800–61,100.