Frequency-swept Ferromagnetic Resonance Characterization of Permalloy Thin Films

Samuel Holladay

EECS Department
University of California, Berkeley
Technical Report No. UCB/EECS-2018-53
May 11, 2018

http://www2.eecs.berkeley.edu/Pubs/TechRpts/2018/EECS-2018-53.pdf

The dynamic properties of permalloy thin films were studied with vector network analyzer based ferromagnetic resonance (VNA-FMR). Resonance was excited in the magnetic samples with coplanar waveguides (CPWs), and the resulting absorption change was analyzed in the frequency domain to yield the magnetization and damping of the measured samples. Two different VNA-FMR setups are discussed: one system uses a flip-chip geometry in which the magnetic sample is placed on top of a relatively large CPW, while the other uses a microwave probe station to contact smaller CPWs that were deposited and lithographically patterned on top of the magnetic sample. The flip-chip setup is shown to be capable of conducting broadband, frequency-swept FMR measurements in the in-plane (IP) and out-of-plane (OOP) orientations, and is validated with measurements of permalloy (Py) thin films. A transition from IP to OOP resonance is observed by applying a high magnetic field along the Py sample's hard axis. Finally, the microwave probe setup is evaluated. The method for fabricating CPWs with photolithography and thermal evaporation is discussed, and shown to yield waveguides with low loss and good broadband performance. FMR signals are found to be weaker in this measurement setup due to the smaller change in absorption associated with the smaller device geometries, and it is shown that the strength of the FMR signal is relatively uncorrelated with high-frequency losses in the system.

Advisor: Sayeef Salahuddin


BibTeX citation:

@mastersthesis{Holladay:EECS-2018-53,
    Author = {Holladay, Samuel},
    Title = {Frequency-swept Ferromagnetic Resonance Characterization of Permalloy Thin Films},
    School = {EECS Department, University of California, Berkeley},
    Year = {2018},
    Month = {May},
    URL = {http://www2.eecs.berkeley.edu/Pubs/TechRpts/2018/EECS-2018-53.html},
    Number = {UCB/EECS-2018-53},
    Abstract = {The dynamic properties of permalloy thin films were studied with vector network analyzer based ferromagnetic resonance (VNA-FMR). Resonance was excited in the magnetic samples with coplanar waveguides (CPWs), and the resulting absorption change was analyzed in the frequency domain to yield the magnetization and damping of the measured samples. Two different VNA-FMR setups are discussed: one system uses a flip-chip geometry in which the magnetic sample is placed on top of a relatively large CPW, while the other uses a microwave probe station to contact smaller CPWs that were deposited and lithographically patterned on top of the magnetic sample. The flip-chip setup is shown to be capable of conducting broadband, frequency-swept FMR measurements in the in-plane (IP) and out-of-plane (OOP) orientations, and is validated with measurements of permalloy (Py) thin films. A transition from IP to OOP resonance is observed by applying a high magnetic field along the Py sample's hard axis. Finally, the microwave probe setup is evaluated. The method for fabricating CPWs with photolithography and thermal evaporation is discussed, and shown to yield waveguides with low loss and good broadband performance. FMR signals are found to be weaker in this measurement setup due to the smaller change in absorption associated with the smaller device geometries, and it is shown that the strength of the FMR signal is relatively uncorrelated with high-frequency losses in the system.}
}

EndNote citation:

%0 Thesis
%A Holladay, Samuel
%T Frequency-swept Ferromagnetic Resonance Characterization of Permalloy Thin Films
%I EECS Department, University of California, Berkeley
%D 2018
%8 May 11
%@ UCB/EECS-2018-53
%U http://www2.eecs.berkeley.edu/Pubs/TechRpts/2018/EECS-2018-53.html
%F Holladay:EECS-2018-53