New publication!- N. Kani, J. T. Heron, A. Naeemi, IEEE Trans. Mag. Accepted (2017).

Abstract:
Recent experiments have shown the ability to introduce an anisotropy energy to the energy landscape of a thin-film nanomagnet through the use of mechanical strain. Assuming this strain-induced anisotropy is large enough, the low-energy state of the nanomagnet is altered and can be used to initialize the magnetization along a given axis. Utilizing this effect, we propose a more energy efficient method of nanomagnet reversal through spin-transfer torque (STT). This is accomplished by first initializing the magnetization to a high-energy state, and then applying a short current pulse to nudge the magnetization in the appropriate energy basin. Using extensive numerical simulations, we qualitatively analyze this type of reversal and find the optimal parameters for reliable functionality while in the presence of thermal noise. We demonstrate that despite negating the initial portion of nominal STT reversal, where the STT must fight against the damping torque of the initial energy-basin, the magnitude of spin current required for our proposed strain-mediated reversal is equivalent to the nominal case. However, the strain-meditated reversal is beneficial by minimizing the spin-current pulsewidth necessary for reliable operation allowing for large energy savings. Assuming the strain-anisotropy is significantly larger than the nanomagnet’s internal free-axis anisotropy, strain-mediated reversals offer a 10 energy reduction over nominal STT reversals.

The full manuscript is available from IEEE Transactions on Magnetics.

Assistant professor John Heron has been appointed as an M-Write fellow for Fall 2017. M-Write aims to transform the teaching and learning across the University of Michigan through increased student engagement and transformative learning. M-Write implements a writing-to-learn pedagogy with the incorporation of an automated peer review process. The writing-to-learn pedagogy is unique in that it seeks to supplement mathematical understanding of core concepts with written expression of understanding. Students are posed with a writing prompt designed to test the understanding of a core class principle and the ability to express it. The peer review process encompasses critique and revision steps which enable students to engage with one another for peer-to-peer learning. The ability to express technical concepts through writing and oral presentations have become critical skills for modern scientists and engineers. M-Write is used in material science and engineering courses in order to build some of these skills.

The first infusion of M-Write into the materials science and engineering curriculum came in the spring of 2016. Professor Rachel Goldman piloted the program in the introductory materials science course MATSCIE 250, where students wrote about several key concepts including the interpretation of phase diagrams, polymer recycling and its impact on mechanical properties,[1] and corrosion as it relates to the recent Flint water crisis. With funding from the Center of Research on Teaching and Learning, Professor Heron along with collaborators Professors Goldman and Kioupakis, and Dr. Chambers, developed an “M-Write Electronic Materials sequence”, in which a “spiral” approach to the instruction of quantum mechanical concepts were fostered through writing-to-learn pedagogies. The course sequence included MATSCIE 242 (Physics of Materials), MATSCIE 400 (Electronic, Magnetic, and Optical Materials), and MATSCIE 500 (Materials Physics and Chemistry).

In the Fall 2017 semester, professor Heron will implement M-Write in the introductory materials science course MATSCIE 220. Throughout the semester, he and a graduate student instructor will become engaged with faculty and students across campus to participate in a semester long seminar that will focus on the development of writing prompts and methodologies for enhanced student involvement.

For further information about M-Write, go to http://lsa.umich.edu/sweetland/m-write.html

[1]  “Investigation of the influence of a writing-to-learn assignment on student understanding of polymer properties” S.Finkenstaedt-Quinn, A. Halim, T. Chambers, A. Moon, R.S. Goldman, A.R. Gere, and G. Shultz, The Journal of Chemical Education, accepted (2017).

Research Education and Activities for Classroom Teachers is an event where grade school teachers from around Michigan can come and attend workshops to participate in materials science labs that they can then take back to their respective classrooms. Peter helped develop and run the “Introduction to Composite Materials” demo at REACT, where students (teachers) made their own composite concrete mixtures and tested the mechanical properties. The goal of the lab is to get students thinking about how different reinforcement materials can impart different properties into the composites and about how to optimize a material for a given application.

Xplore Engineering is an outreach event designed for alumni and the children in their life entering the 4th through 7th grade. Through a series of experiential workshops, participants get hands-on experience in a variety of engineering disciplines.

Through the materials science department, Peter helped run the eXtraordinary Materials workshop where kids got to investigate the structure of common materials through optical and electron microscopy and learn about how materials can behave unexpectedly at really hot or really cold temperatures. Demos included heating a space shuttle tile with a blowtorch, heating an iron wire and observing the high temperature phase change, and cooling rubber through the glass transition temperature with liquid nitrogen so it becomes more brittle and eventually shatters.

Brandi is a rising senior at Cal Poly Pomona studying physics with an emphasis in optics. At her home campus, she conducts research on biconically tapered optical fibers used in biological sensing applications. She is at the University of Michigan this summer to participate in a NSF funded REU hosted by the Center of Photonics and Multiscale Nanomaterials. While not doing research, Brandi enjoys exploring Ann Arbor, reading in the park or eating great food.

Brandi is working with Peter on the investigation of spintronic phenomena in chalcogenide thin films.