CAREER: Magnetization Dynamics and Damping in Magnetic Nanostructures

Tim Mewes, University of Alabama Tuscaloosa, DMR 0952929

This Faculty Early CAREER award funds research to investigate the magnetization dynamics and damping of magnetic nanostructures. The broadband ferromagnetic resonance capabilities, that have been developed as part of this grant, have been used to investigate a number of different material systems during the current funding period. Our work on structural and magnetic properties of Cr-diluted CoFeB has been published and our work on magnetic damping in Co2FeAl films has been accepted for publication. We have also used our capabilities to determine the exchange stiffness of thin YIG films. We utilized our angle dependent and broadband FMR capabilities to determine the demagnetization factors of thin films with surface roughness and to investigate the relaxation processes in epitaxial CoxFe3-xSi films.A better understanding of the magnetization dynamics and the relaxation in these and other systems is crucial for many spintronic applications.

For a YIG film grown using liquid phase epitaxy the exchange field determined at various microwave frequencies is plotted as a function of the square of the mode number. The inset shows a typical FMR spectrum measured at 20 GHz.

Demagnetization factors Nxx, Nyy and Nzz determined using a combination of in-plane angular dependent and frequency dependent FMR measurements as a function of inverse film thickness for Co90Fe10 deposited on a rippled substrate.

b)In-plane angular dependence for an epitaxial Co1.75Fe1.25Si 20nm thin film of a) the ferromagnetic resonance field and b) the corresponding resonance linewidth measured at 30GHz. While the resonance field is consistent with a uniaxial and four-fold anisotropy of the film, the linewidth exhibits a clear four-fold symmetry.

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CAREER: Magnetization Dynamics and Damping in Magnetic Nanostructures

Tim Mewes, University of Alabama Tuscaloosa, DMR 0952929

During summer 2014 two high school students worked in the group of the PI. During the same time period Lisa Gareis, an undergraduate student from the University of Kaiserslautern (Germany) carried out investigations of Yittrium Iron Garnet (YIG) samples in our group. We currently also have a visiting graduate student from Thailand working in our group for six months. The PI also reached out to a local elementary school with some hands-on demonstrations about electricity.During summer 2014 the PI organized again the summer program of the MINT Center. This program brings local High School students together with undergraduate students, both from within the United States and from abroad, to do research for nine weeks with faculty, postdocs and graduate student mentors at the MINT center.The research and development of broadband ferromagnetic resonance capabilities continues to have a significant impact on the field of spintronics and are important for the development of future technology in this area.

Two high school students workingtogether with a graduate student.

Visiting undergraduate student LisaGareis from Kaiserslautern, Germany.

Hands-on demonstration of electricity at alocal elementary school.

Visiting graduate student Pirat Khunkittifrom Thailand.

Summer program award ceremony for High School and international students