Effect of Laser Annealing on Permeability Spectra in Co-based Amorphous Ribbon

We investigated the variation of permeability spectra and relaxation frequency in Co-based amorphous ribbon annealed by pulsed Nd:YAG laser at various annealing energy Ea. The complex permeability spectra varies sensitively with the annealing energy, where the spectra could be decomposed into two contributions from domain wall motion,μdw(f) and rotational magnetization μrot(f) by analyzing the measured spectra as a function of driving ac field amplitude. The magnitude of μdw(f) and μrot(f) in dc limit shows maximum at Ea = 176 mJ. The maximum relaxation frequency for rotational magnetization, determined by μ'(f) curve, is about 700 kHz at Ea=62 mJ but that for wall motion is about 26 kHz at 230 mJ. These variations reflect the increase of magnetic softness and microstructural change by the annealing.

Flexible tuning microwave permeability spectrum in [ferromagnet/antiferromagnet]_n exchange-biased multilayer stack structure

NiFe/[IrMn/NiFe/IrMn] 5 /[NiFe/IrMn] 4 /NiFe structured exchange-biased multilayer films are designed and prepared by magnetron sputtering. The static and the microwave magnetic properties are systematically investigated. The results reveal that adding a partially pinned ferromagnetic layer can effectively broaden the ferromagnetic resonance linewidth toward the low frequency domain. Moreover, a wideband multi-peak permeability spectrum with a 3.1-GHz linewidth is obtained by overlapping the spectra of different partially pinned ferromagnetic layers and [antiferromagnet/ferromagnet/antiferromagnet] n stacks. Our results show that the linewidth of the sample can be feasibly tuned through controlling the proper exchange bias fields of different stacks. The designed multilayered thin films have potential application for a tunable wideband high frequency noise filter.

HIGH-TEMPERATURE AC MAGNETIC PROPERTIES OF NANOCRYSTALLINE FINEMET ALLOYS WITH Co ADDITION

High-temperature AC magnetic properties for （Fe0.5Co0.5）73.5Cu1Nb3Si13.5B9 alloy annealed at various temperatures have been investigated using an impedance analyzer. Annealing temperature Ta has obvious effects on high-temperature AC magnetic properties of the alloy. The Hopkinson peak appears only in the amorphous alloy when Ta≤703K. As Ta increases above 733K, the real part of the complex initial permeability μi′descends gradually, μi′decreases more slowly with temperature in the high temperature range. The high-temperature （about 750K） AC initial permeability for the alloy annealed at Ta= 763K has been found to maintain a stable high value of 950 up to a frequency of- 1 × 10^5Hz. Partial substitution of Co for Fe in the F73.5Cu1Nb3Si13.5B9 alloy leads to an increase of around 110K of the Curie temperature of the amorphous phase, much higher than Ge-containing Finemet alloy.

High-frequency magnetic properties of biphase Ce_(2)Fe_(17)N_(3)/α-Fe microflakes with easy-plane anisotropy

Soft magnetic composites(SMCs)are effective as magnetic powder cores in an inductor.Due to high saturation magnetization,large magnetocrystalline anisotropy and high operating frequency of M(metal)-RE(rear earth)soft magnetic composites,it is possible to miniaturize inductor cores by reducing total loss,especially eddy current loss and excess loss at high frequencies.In this article,the characteristics of Ce_(2)Fe_(17)N_(3)/α-Fe(CFN/F)loss per volume and effective permeability reaching a high frequency of 3 MHz are investigated.The biphase CFN/F composite exhibits a high permeability of 16 at 70 MHz,which is two times greater than that of pure Ce_(2)Fe_(17)N_(3)(CFN)powders.The total loss is as low as 545 mW/cm^(3)at 3 MHz and 6 mT.The direct current(DC)-bias properties have a percent of permeability exceeding 65% at H=7960 A/m.This phenomenon indicates that our material has a higher working frequency and lower core loss than other materials;the biphase CFN/F structure is a promising and efficient approach for developing the miniaturized radio frequency(RF)inductor core.