Magnetic and high frequency properties of nanogranular CoFe-TiO2 films

Abstract

A series of soft magnetic nanogranular CoFe-TiO2 films with different thicknesses were fabricated on Si substrates by co-sputtering CoFe and TiO2, and the magnetic and high frequency properties were studied in details. X-ray diffraction analysis confirmed that the films were nanocrystalline/amorphous composites. A saturation magnetization as high as 21 kGs and a ferromagnetic resonance (FMR) frequency above 3 GHz were obtained. It was found that the coercivity decreased steeply with the increase of film thickness and its minimum value was about 6 Oe. In addition, the variations of FMR peak broadness of the imaginary part and damping factor were also presented and discussed as functions of film thickness.

High frequency characteristics of (Ni 75 Fe 2 ) x (ZnO) 1− x granular thin films with tunable damping coefficient

“…[13][14][15] The damping factor α eff also shows the similar trend with ∆ f . As reported previously, [9,15] α eff is generally divided into two parts: intrinsic part α in and extrinsic part α ext , and α eff = α int + α ext . The α int contributes to fundamental properties like the Zeeman transition, crystallographic or magnetic structure, while the two-magnon scattering and the local anisotropy dispersion contribute significantly to α ext .…”

“…So any study of the damping factor, especially of how to tune α, is very significant for future applications. Several studies were conducted of the contributions of different preparation technologies to the damping factor, including alternatives for fabricating the underlayer, [5] fabrication conditions, [6][7][8] changing the film thickness, [9] and magnetic field annealing. [10] However, studies related to the dependence of magnetization dynamics on the volume fraction of the ferromagnetic metal in a granular film system are still lacking.…”

Compositional dependence of magnetic and high frequency properties of nanogranular CoFe-Yttrium-doped Zirconia films

“…The further decrease in grain size caused most of the magnetic granules to become covered in a thick YSZ thick layer. Although intergranular exchange coupling could still exist through the electron tunneling spin polarization propagating across this YSZ barrier [25], the exchange interaction was weakened. This very likely disrupted the degree of ordering of the magnetic moments.…”

Marked Enhancement of Roll-Off Frequency in FeCoN Synthetic Antiferromagnetic Films Deposited by Oblique Incidence

“…But FeCo thin films with isotropic magnetic properties are not applicable for high frequency applications. Many efforts have been adopted to increase the H k of FeCo thin films, such as applying an induced magnetic field during film deposition [6], depositing on prestressed substrates [7] or flexible substrates [8], field annealing [9], stress inducing [10], oblique deposition [11], micro strip patterning [12], introducing gradient of the Hf concentration [13,14] and using an organic semiconductors underlayer [15]. However, it is still a big challenge getting a very large H k in soft magnetic films and enhancing their f r beyond 5 GHz.…”