Tunable zero-field ferromagnetic resonance frequency from S to X band in oblique deposited CoFeB thin films

Abstract

Tunable zero-field ferromagnetic resonance frequency in wide range is very useful for the application of microwave devices. We performed an investigation of the static and high frequency magnetic properties for oblique sputtered CoFeB thin films. The static magnetic results revealed that oblique sputtered CoFeB thin films possess well defined in-plane uniaxial magnetic anisotropy, which increases monotonically from 50.1 to 608.8 Oe with the increasing of deposition angle from 10° to 70°. Continuous modification of the resonance frequency of CoFeB thin films in a range of 2.83–9.71 GHz (covers three microwave bands including S, C and X bands) has been achieved. This behavior can be explained as the result of the microstructure due to the self-shadowing effect mainly. These CoFeB thin films with tunable magnetic properties may be good candidates for usage in microwave devices.

Zero-field Optic Mode Beyond 20 GHz in a Synthetic Antiferromagnet

“…Ru is chosen as the spacer layer material due to the strong interlayer coupling it can support [34]. Co 0.2 Fe 0.6 B 0.2 is selected as the ferromagnetic component as significant literature exists on the high-frequency properties of Co-Fe alloys containing B [17,18,[43][44][45]. Ta is used as a seed layer, with Pt or Pd used as a capping layer to inhibit oxidization of the films.…”

“…Conventional methods of accomplishing this goal involve using materials with a high-saturation magnetization 4π M s or increasing H k . From a material selection point of view, the focus of the community has pivoted toward ferrites such as CoFe-based materials [17][18][19]. Enhancements to H k are typically achieved through the application of a magnetic field during deposition with potential use of annealing [20], tailoring the nanocrystalline structure of the films using chemical stress or oblique sputtering [17,21], use of prestressed substrates [22], or lamination and lithographic patterning [14].…”

“…Exchange-biased systems have also been proposed [23]. The highest frequencies in self-bias systems achieved to date are in the X -band range, around 10 GHz [17,23]. There are notable difficulties in further tailoring of H k using the methods outlined above, such as the application of a dc field during depositions, which induces an anisotropy that is difficult to modify and prestressed substrates requiring mechanical flexibility.…”

Patterned FeNi soft magnetic strips film with tunable resonance frequency from 1 to 10.6 GHz

“…Resonance frequency ( f r ) is the most important factor which affects applications of these soft magnetic films. To obtain a higher f r and its wider tunable range are the primary objectives for many studies 4 7 8 . Based on the Kittle equation , there are two factors to determine the f r of the films, the saturation magnetization ( M s ) and anisotropy filed ( H k ) also called the in-plane uniaxial magnetic anisotropy (IPUMA) field 6 .…”

Tailoring the soft magnetic properties of sputtered multilayers by microstructure engineering for high frequency applications

“…temperature, pressure, power, etc.). [8][9][10][11] Moreover, it is well known that the amount of disorder at the surfaces and interfaces, which is also influenced by process parameters, can greatly disturb the soft magnetic properties of thin films, such as coercivity, magnetic domain structure, magnetization reversal and magnetic anisotropy. [12][13][14][15][16][17] Therefore, when tailoring the soft magnetic multilayers for high-frequency operation it is important to predict and control the microstructure and surface/interface roughness.…”