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Developing a temperature sensitive tool for studying spin dissipation

Wickey, Kurtis J

Abstract Details

2015, Doctor of Philosophy, Ohio State University, Physics.
Measuring the thermodynamic properties of nanoscale structures is becoming increasingly important as heterostructures and devices shrink in size. For example, recent discoveries of spin thermal effects such as spin Seebeck and spin Peltier show that thermal gradients can manipulate spin systems and vice versa. However, the relevant interactions occur within a spin diffusion length of a spin active interface, making study of these spin thermal effects challenging. In addition, recent ferromagnetic resonance studies of spatially confined nanomagnets have shown unique magnon modes in arrays and lines which may give rise to unique magnon-phonon interactions. In this case, the small volume of magnetic material presents a challenge to measurement and as a result the bulk of the work is done on arrays with measurements of the magnetization of individual particles possible through various microscopies but limited access to thermal properties. As a result, tools capable of measuring the thermal properties of nanoscale structures are required to fully explore this emerging science. One approach to addressing this challenge is the use of microscale suspended platforms that maximize their sensitivity to these spin thermal interactions through thermal isolation from their surroundings. Combining this thermal decoupling with sensitive thermometry allows for the measurement of nanojoule heat accumulations, such as those resulting from the small heat flows associated with spin transport and spin relaxation. As these heat flows may manifest themselves in a variety of spin-thermal effects, the development of measurement platforms that can be tailored to optimize their sensitivity to specific thermal measurements is essential. To address these needs, I have fabricated thermally isolated platforms using a unique focused ion beam (FIB) machining that allow for flexible geometries as well as a wide choice of material systems. The thermal characteristics of these platforms were rigorously tested by measuring the heat capacity of a 6.2 ng Au sample using a microscale suspended SiNx platform. The heat capacity measurement was selected for its ability to provide meaningful metrics in the evaluation and optimization of our platform design. The results match closely with the values obtained for bulk samples despite a 10^12 difference in mass and our platforms perform near the state-of-art for thin film calorimetry. Having established the sensitivity of the SiNx platforms, I designed and built a custom vacuum setup for use in a microwave cavity for the thermal measurement of resonant spin dynamics. The long term goal is to thermally study the resonant spin transfer across a FM/N interface utilizing the decay of the spin polarization through magnon-phonon and electron-phonon interactions. Initial measurements were done and challenges identified and improvements suggested.
Ezekiel Johnston-Halperin (Advisor)
Fengyuan Yang (Committee Member)
Mohit Randeria (Committee Member)
Harris Kagan (Committee Member)
140 p.

Recommended Citations

Citations

  • Wickey, K. J. (2015). Developing a temperature sensitive tool for studying spin dissipation [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1437252889

    APA Style (7th edition)

  • Wickey, Kurtis. Developing a temperature sensitive tool for studying spin dissipation. 2015. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1437252889.

    MLA Style (8th edition)

  • Wickey, Kurtis. "Developing a temperature sensitive tool for studying spin dissipation." Doctoral dissertation, Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1437252889

    Chicago Manual of Style (17th edition)