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ECE Colloquium Series – Professor Shaloo Rakheja
October 11, 2018 @ 3:45 pm - 5:15 pm
As part of the *Eleanore Hale Wilson Lecture Series, ECE is proud to present:
Physics, Modeling, and Applications of Stochastic Magnetization Dynamics in Magnetic Nanostructures
Professor Shaloo Rakheja
New York University
Host: Professor Marc Riedel
Random thermal effects on magnetization dynamics have been studied for several decades, since the seminal research conducted by Néel [C.R. Acad. Sci. Paris 228, 664 (1949)] and Brown [Phys. Rev. 130, 1677 (1963)], and more recently reviewed by Coffey and Kalmykov [Jour. App. Phys., 112, 121301 (2012)] for fine ferromagnetic bodies with uniaxial and cubic anisotropy. This continuous interest in stochastic magnetization dynamics has been motivated by numerous scientific and technological applications, which range from the study of thermally activated switching in magnetic data storage devices to the analysis of power spectral density of spin-torque nano-oscillators in the area of spintronics.
In this talk, I will discuss the purity of randomness in a magnetic tunnel junction in which a dissipative spin torque is used to excite precessional dynamics and, consequently, relax the magnetization toward one of its two stable points in a random fashion. I will begin by describing the classical model of magnetization dynamics in which thermal effects are included via two distinct and disjoint terms in the effective field of the macroscopic equation of motion: (a) a dissipative field and (b) a random thermal field. I will show that the classical method becomes inadequate for explaining low temperature (10m K—10 K) phenomena, such as macroscopic tunneling of magnetization in which the transition rate between two magnetic states is independent of temperature. By modeling the dynamics due to thermal effects using a single random process composed of discontinuous transitions (jumps) with Poisson arrivals, called the jump-noise, a unified model applicable over a broad range of temperatures is obtained. The jump noise provides a justification for quantum tunneling of magnetization without invoking quantum mechanics. Equivalence between the jump-noise and classical dynamics of magnetic bodies will be established.
I will discuss applications of the jump-noise model to explain magnetoelectric switching of antiferromagnetic (AFM) order parameter, in particular, the AFM state in single-domain Cr2O3, which can be electrically switched to enable an ultra-low-power and ultra-fast substrate for computing and memory applications. I will close my talk by briefly highlighting our recent work investigating (i) power-accuracy trade-off in approximate spintronic circuits and (ii) security implications of an image processing spintronic IP against approximate Boolean satisfiability attacks.
Dr. Shaloo Rakheja is currently an assistant professor of the electrical and computer engineering department at New York University (NYU). Prior to joining NYU in 2015, she was a postdoctoral associate at the Microsystems Technology Laboratories at Massachusetts Institute of Technology. She received her M.S. and Ph.D. degrees in electrical and computer engineering from the Georgia Institute of Technology in 2009 and 2012, respectively.
Her current research focus is modeling and simulation of nanoelectronic and spintronic devices for energy-efficient computing. She has successfully attracted funding from the National Science Foundation, Semiconductor Research Corporation, and industry for her research in terahertz spintronics, plasmonics, and wide bandgap semiconductors for RF applications. She has received multiple awards including the prestigious 2018 NYU Goddard Junior Faculty Fellowship, the NSF Career Research Initiation Award in 2016, the Intel PhD Fellowship for the academic year 2011-2012, and the ECE Graduate Research Assistant Excellence Award for the academic year 2011-2012.
In her spare time, Shaloo enjoys reading (mystery) novels, writing poetry, and visiting museums.
*Established in 2009, the Eleanore Hale Wilson Fund supports engineering field leaders for travel to Minnesota to share their expertise and discoveries with University of Minnesota graduate students, faculty, and alumni. The fund also supports the receptions held in honor of each speaker.