Magnetic thin films are widely used for high-speed electronics, such as information storage, electromagnetic compatibility, magnetic field sensors, and microwave communication devices due to the miniature size, light weight, well maintained structure, and most importantly, high microwave permeability. This project includes three subjects.

Reason for high microwave permeability
It is well-known that magnetic thin films potentially possess high microwave permeability. It has been considered that specific shape would induce high permeability of thin films. However, not all thin films have promising microwave properties. Therefore, it is necessary to theoretically understand the reasons behind the high microwave permeability in magnetic thin films.

Characterization of thin film permeability in GHz range
An easy and precise method for measurement of frequency dependent complex permeability is important to effectively characterize magnetic thin films. At GHz frequencies, transmission line methods are mostly used. In this work, we designed a simple one-port strip line permeameter. Using this fixture, we can analytical deduce the complex permeability of ferromagnetic films over 0.1 - 5 GHz.

Deposition of thin films with desired high-frequency properties
High-frequency complex permeability, determined by ferromagnetic resonance, is one of the most important properties of magnetic thin films used for microwave applications. To obtain high microwave permeability, both the frequency and the amplitude of the resonance should be as high as possible. These quantities are dependent on the composition, crystalline and magnetic structure of the materials. Here, we focus on studying the effect of composition and magnetic structure on microwave permeability.

In addition, high resistivity or low permittivity is needed for high frequency applications. However, the resistivity of metallic magnetic materials is too low to avoid eddy current loss. In this light, we will experimentally explore the strategies to reduce the eddy current loss of magnetic thin films.