Proposal Number CTS-0625314 Principal Investigator Asheghi, Mehdi Affiliation Carnegie-Mellon University Proposal Title Giant Magneto Thermal Resistance (GMTR) Phenomenon
The GMR multilayer structure can display relatively large changes in its electrical resistivity (in the presence of a magnetic field), while the GMTR effect is referred to "giant" changes in thermal conductivity under a magnetic field. Although the electrical and magnetic properties of the GMR structures have been the subject of extensive research in the past two decades, the fundamentals of the thermal transport in these layers have received very little attention. This research will provide a more in-depth understanding of the physics of nanoscale energy transport in Giant Magnetoresistance (GMR) multilayers through comprehensive and systematic experimental measurements of its transport properties. Comprehensive thermal characterization of the GMR multilayers in both the in-plane and out-of-plane directions will be performed as a function of (a) temperature (20-450 K), (b) magnetic field, and (c) superlattice period, thickness and composition. Steady state and transient electrical-resistance thermometry techniques will be used for in-plane thermal conductivity and heat capacity measurements. The out-of-plane thermal conductivity will be measured using the thermoreflectance technique.
Intellectual Merit: This study can potentially provide the groundwork for invention of a new generation of thermally based magnetic sensors as well as ultra-fast thermal switches capable of modulating or controlling the flow of heat at time scales in the order of ~ 10 ns with on-off states for thermal resistances that may differ by nearly an order of magnitude. Since multilayered metallic films (e.g., Co, Pt, FeCo), consisting of repeats of ~10 thickness, have found vast applications in thermally assisted magnetic recording, or Magnetic Random Access Memory (MRAM) devices, the results of the proposed research can have a large impact on emerging high density data storage technologies.
Broader Impacts: This program has a substantial emphasis on high school and undergraduate research and education, in particular among women and minorities. An ambitious plan is proposed to educate and train 5 students with the specific goal of preparing and positioning them to pursue graduate studies at the top tier universities. This requires extensive involvement in research conducted at the Micro/Nano-scale Heat Transfer Laboratory and close collaboration with graduate students. In order to disseminate our knowledge and share our state-of-the-art micro/nano-scale heat transfer laboratory, we propose to establish a web-based infrastructure such that a remote user would be able to take advantage of the experimental facility in real time. This will be the centerpiece of our outreach program as it provides the groundwork and infrastructure for future educational and research activities.
