Dongsheng Yao

Grain size dependence of coercivity in magnetic metal-insulator nanogranular films with uniaxial magnetic anisotropy

Excellent soft magnetic properties and appropriate uniaxial magnetic anisotropy field have been achieved in a wide metal volume fraction (x) range for as-deposited (Fe65Co35)x(SiO2)1−x granular films fabricated by magnetron sputtering. With decreasing x from 0.86 to 0.53, the coercive force of easy axis Hce decreases clearly and shows the minimum value (Hce=0.85 Oe) at x=0.53. More importantly, not only nanoscale grain-size D contributing to small coercivity is proved, but also a D3 dependence of Hce is observed in the range of 0.53<x<0.86, which is similar to the results of Suzuki et al. reported for nanocrystalline alloys. Based on the random anisotropy model of Suzuki and Herzer, the grain-size D dependence of coercivity Hce in our metal-insulator granular film system was analyzed. Analyze results indicate that strong coherent uniaxial anisotropy which dominates over the random anisotropy ⟨K1⟩ of magnetic grains obtained by the random anisotropy model can be responsible for the D3 dependence of the coe...

Controlling the microwave characteristic of FeCoB-ZnO granular thin films deposited by obliquely sputtering

A series of FeCoB-ZnO soft magnetic granular films deposited at different oblique angles were prepared by magnetron sputtering system. A variable in-plane uniaxial magnetic anisotropy field from 27.6 Oe to 212 Oe and an adjustable ferromagnetic resonance frequency from 1.89 GHz to 5.3 GHz were obtained in the as-deposited films just by increasing the oblique angle from 15° to 56°. Frequency line-width and effective Gilbert damping factor were both insensitive to the different oblique angles (αeff decreased from 0.036 to 0.03 and Δf decreased from 1.49 to 1.27), which almost satisfied the requirement that fFMR could be tuned independently in a certain frequency range. Besides, the change of dynamic magnetic anisotropy field versus oblique angle was illustrated and analyzed quantitatively compared with the static magnetic anisotropy.

Modulation of the Acher’s limit by medium thickness in [FeCoB/ZnO]50 multilayers

Abstract This work investigates the high frequency characteristics of [FeCoB/ZnO]50 multilayers with different ZnO thickness. The results reveal that the Acher’s limit of [FeCoB/ZnO]50 multilayers can be modulated by medium thickness. Increasing medium layer thickness is favorable for breaking through the Acher’s limit. It is found that the differences of Acher’s limit between multilayers and single layers are caused by magnetic interface anisotropy related to interface roughness and some unknown factor. Graphical Abstract