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

Chengyi Li,Guozhi Chai,Chengcheng Yang,Desheng Xue,Wenfeng Wang

doi:10.1038/srep17023

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.

Highlights

Magnetic materials are widely used in many microwave devices, such as magnetic sensors, energy harvesters, phase shifters, tunable filters and so on[1,2,3], Compared with bulk materials, magnetic thin films, which have higher in-plane anisotropy, are widely studied in many works[4,5,6], Most of the recent works focus on pushing the resonance frequency fr of films to over 5 GHz, it is still a challenge to find a method to push the resonance frequency of thin films to much higher level and adjust the fr in a wide frequency range simultaneously[7,8,9]
CoFe alloy, which is one of the magnetic materials with largest saturation magnetization, is widely investigated in magnetic thin films[20,21,22,23], Among these works, the Ru/FeCoB double layered film indicates that large anisotropy can be induced in FeCoB layer[24], In
The peak positions of all of the films in the diffraction spectra almost keep the same around 45.20°, which agrees with the (110) diffraction peaks of BCC Co7Fe3 with Powder Diffraction File (PDF) number 50–0795. This shows that the films are all BCC structure, and the lattice spacing does not changed with the oblique deposition changing

Summary

Introduction

Magnetic materials are widely used in many microwave devices, such as magnetic sensors, energy harvesters, phase shifters, tunable filters and so on[1,2,3], Compared with bulk materials, magnetic thin films, which have higher in-plane anisotropy, are widely studied in many works[4,5,6], Most of the recent works focus on pushing the resonance frequency fr of films to over 5 GHz, it is still a challenge to find a method to push the resonance frequency of thin films to much higher level (for example, X band) and adjust the fr in a wide frequency range simultaneously[7,8,9]. The Hc along easy axis increases with the increasing oblique angle, which is a common result in oblique deposited thin films[28], Fig. 2(d) shows the remanent magnetization curve (Mr/Ms) of films with different deposited angles.

Results

Conclusion