Bulletin of the American Physical Society
APS March Meeting 2013
Volume 58, Number 1
Monday–Friday, March 18–22, 2013; Baltimore, Maryland
Session J14: Magnetic Devices and Techniques |
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Sponsoring Units: GMAG Chair: Mohammad Fashami, The Virginia Commonwealth University Room: 316 |
Tuesday, March 19, 2013 2:30PM - 2:42PM |
J14.00001: Implications of stochastic magnetization dynamics on reliability of dipole coupled nanomagnetic logic Mohammad Salehi Fashami, Jayasimha Atulasimha, Supriyo Bandyopadhyay Straintronic nanomagnetic logic (SML), where Boolean computation is elicited from dipole coupled multiferroic nanomagnets switched with electrically generated strain, has emerged as an extremely energy-efficient computing paradigm. We have studied the reliability of such logic circuits by computing the gate error rates in the presence of thermal noise by simulating switching trajectories with the stochastic Landau-Lifshitz-Gilbert (LLG) equation. In addition, we examine the lower bound of energy dissipation as a function of switching error and explain how the out-of-plane excursion of the magnetization vector leads to excess energy dissipation over this bound for a given switching error. This analysis is performed to understand the connection between reliability and energy dissipation for a single switch and then extended to larger nanomagnetic logic circuits to assess the viability of dipole coupled SML. [Preview Abstract] |
Tuesday, March 19, 2013 2:42PM - 2:54PM |
J14.00002: Experimental realization of straintronic nanomagnetic logic using strain-induced magnetization switching in magnetostrictive nanomagnets elastically coupled to PMN-PT Noel D'Souza, Mohammad Salehi-Fashami, Supriyo Bandyopadhyay, Jayasimha Atulasimha Single-domain magnetostrictive Ni nanomagnets are grown on a bulk \textless 001\textgreater\ PMN-PT substrate and their domain switching is studied through Magnetic Force Microscopy (MFM) and Scanning Electron Microscopy with Polarization Analysis (SEMPA) techniques. By applying a voltage across the length of the PMN-PT substrate ($d_{33}$ coupling), a mechanical strain is applied along the nanomagnet's easy axis of magnetization resulting in domain switching and is investigated for several scenarios. First, the magnetization switching of single, isolated nanomagnets of various sizes is observed. This is followed by studying the dipole interactions through anti-ferromagnetic (AF) and ferromagnetic (F) coupling. The accurate, unidirectional propagation of the magnetization state is also investigated through an array of three AF-coupled nanomagnets. Finally, NAND logic operation using these nanomagnets is explored. Since SEMPA analysis involves no alteration of a sample's magnetic state, unlike in MFM imaging, we also analyze these scenarios using this technique at NIST, Gaithersburg. [Preview Abstract] |
Tuesday, March 19, 2013 2:54PM - 3:06PM |
J14.00003: ABSTRACT WITHDRAWN |
Tuesday, March 19, 2013 3:06PM - 3:18PM |
J14.00004: Single Circuit Parallel Computing with Phonons through Magneto-acoustics Sophia Sklan, Jeffrey Grossman Phononic computing \textendash{} the use of (typically thermal) vibrations for information processing \textendash{} is a nascent technology; its capabilities are still being discovered. We analyze an alternative form of phononic computing inspired by optical, rather than electronic, computing. Using the acoustic Faraday effect, we design a phonon gyrator and thereby a means of performing computation through the manipulation of polarization in transverse phonon currents. Moreover, we establish that our gyrators act as generalized transistors and can construct digital logic gates. Exploiting the wave nature of phonons and the similarity of our logic gates, we demonstrate parallel computation within a single circuit, an effect presently unique to phonons. Finally, a generic method of designing these parallel circuits is introduced and used to analyze the feasibility of magneto-acoustic materials in realizing these circuits. [Preview Abstract] |
Tuesday, March 19, 2013 3:18PM - 3:30PM |
J14.00005: Giant magnetoimpedance effect of Co-based magnetic ribbon as a chemical sensing probe Alejandro Ruiz, Jagannath Devkota, Pritish Mukherjee, Hariharan Srikanth, Manh-Huong Phan The giant magnetoimpedance (GMI) effect consists of a large change in the AC impedance of a soft ferromagnetic conductor subject to an external dc magnetic field that forms the basis for developing a new generation of magnetic sensors. Since the impedance of a soft ferromagnetic material is a function of the skin depth at radio frequency region, the GMI effect of the material can be modified via changes in the resistivity and permeability even at a fixed frequency. This effect arises due to the change in the magnetic anisotropy, material geometry, or electrochemical changes. In the present study, we demonstrate the GMI-based detection of various concentrations of corrosive chemicals using an amorphous Co-based ribbon. Under corrosive fluids, the magnetic permeability and hence the GMI effect of the ribbon changes due to the surface modification of the ribbon. We have found that the GMI ratio decreases with time, reaches a minimum value at a certain time, and then remains almost constant with time. The change in the GMI ratio and the time to achieve a stable value depends on the corrosive strength of the used chemical. These results show promise in developing a new class of chemical sensor using the GMI technology. [Preview Abstract] |
Tuesday, March 19, 2013 3:30PM - 3:42PM |
J14.00006: All-thin-film multiferroic heterostructured cantilevers in linear and nonlinear dynamic regimes Tiberiu-Dan Onuta, Yi Wang, Samuel E. Lofland, Christian J. Long, Ichiro Takeuchi We report on fabrication and characterization of all-thin-film multiferroic magnetoelectric (ME) cantilever devices and their different modes of operation in both linear and nonlinear dynamic regimes. The devices are built on micro-electromechanical system (MEMS) platforms that involve stress-engineered designs based on \textit{silicon oxide/nitride/oxide (ONO)} stacks. The ME layers consist of a magnetostrictive Fe$_{0.7}$Ga$_{0.3}$ thin film and a Pb(Zr$_{0.52}$Ti$_{0.48}$)O$_{3}$ piezoelectric thin film. The resonant frequency was found to display DC magnetic field dependence indicative of the interplay between the anisotropy and Zeeman energies. In the magnetically-driven mode, the harvested peak power at 1 \textit{Oe} is 0.7\textit{ mW/cm}$^{3}$ (RMS) at the resonant frequency (\textit{3.8 kHz}) and the quality factor also displays strong dependence on the DC magnetic bias. In certain conditions, the multiferroic devices show nonlinear behaviors important to logic implementation and parametric amplification. [Preview Abstract] |
Tuesday, March 19, 2013 3:42PM - 3:54PM |
J14.00007: Reliability of Signal Propagation in Magnetostatically Coupled Arrays of Magnetic Nanoelements Reinier van Mourik, Li Gao, Brian Hughes, Charles Rettner, Bert Koopmans, Stuart Parkin Nanomagnetic logic (NML) has promise as a low-power, non-volatile, and radiation resistant alternative to CMOS-based computational devices. Lines of magnetostatically coupled magnetic nano-elements (NEs) propagate information, and the intersections between lines form logic gates. We present simulations and experiments exploring the reliability of signal propagation in NML devices composed of lines of nominally rectangular permalloy NEs, typically 90$\times$60 nm$^2$ in size. An external magnetic field sets the magnetic state of an input bit and also resets each of the NEs' magnetizations along their hard axis direction. As the field is reduced to zero the input state propagates along the line of NEs as they successively relax into one of two equilibrium states. The state of the NEs is probed by (i) a magnetic tunnel junction sensing device integrated with the output NE and (ii) magnetic force microscopy imaging. We conclude that signal propagation is inherently unreliable both through variations in fabrication of the NEs and due to the innate lack of directionality of the flow of information. We demonstrate an alternative clocking method where a domain wall passing underneath an NML device clocks each NE sequentially, thereby increasing the success of signal propagation. [Preview Abstract] |
Tuesday, March 19, 2013 3:54PM - 4:06PM |
J14.00008: Dynamic state switching in nonlinear multiferroic cantilevers Yi Wang, Tiberiu-Dan Onuta, Christian J. Long, Samuel E. Lofland, Ichiro Takeuchi We demonstrate read-write-read-erase cyclical mechanical-memory properties of all-thin-film multiferroic heterostructured Pb(Zr$_{0.52}$Ti$_{0.48})$O$_{3}$ / Fe$_{0.7}$Ga$_{0.3}$ cantilevers when a high enough voltage around the resonant frequency of the device is applied on the Pb(Zr$_{0.52}$Ti$_{0.48})$O$_{3}$ piezo-film. The device state switching process occurs due to the presence of a hysteresis loop in the piezo-film frequency response, which comes from the nonlinear behavior of the cantilever. The reference frequency at which the strain-mediated Fe$_{0.7}$Ga$_{0.3}$ based multiferroic device switches can also be tuned by applying a DC magnetic field bias that contributes to the increase of the cantilever effective stiffness. The switching dynamics is mapped in the phase space of the device measured transfer function characteristic for such high piezo-film voltage excitation, providing additional information on the dynamical stability of the devices. [Preview Abstract] |
Tuesday, March 19, 2013 4:06PM - 4:18PM |
J14.00009: Verification of modified Jiles-Atherton model for determination of hysteresis behavior of materials with two ferromagnetic phases Neelam Prabhu Gaunkar, Cajetan Nlebedim, David Jiles Robust theoretical models of hysteresis are important for describing the properties of ferromagnetic materials. Of the available hysteresis models, the J-A model is widely studied. Efforts have been made to modify and extend the applicability of this model and to improve its accuracy in accounting for different conditions that affect the magnetic state of ferromagnetic materials, such as stress. Recently, the J-A model has been extended to describe the ferromagnetic hysteresis in two-phase magnetic materials. Modeling hysteresis of multi-phase ferromagnetic materials is crucial especially due to the need to develop high performance composite magnetic structures. In this study, the extension of the J-A to accommodate materials with two ferromagnetic phases is experimentally verified. The approach to extracting of the J-A model parameters including saturation magnetization (M$_{\mathrm{s}})$, domain coupling factor ($\alpha )$, domain density (a), reversibility (c) and pinning coefficient (k) in two-phase materials will be presented. [Preview Abstract] |
Tuesday, March 19, 2013 4:18PM - 4:30PM |
J14.00010: Phase encoding technique for super-resolution NV magnetometry Keigo Arai, Chinmay Belthangady, Huiliang Zhang, Stephen DeVience, Ronald Walsworth We report recent progress towards improving the spatial resolution of nitrogen-vacancy-center-based magnetometers by use of phase encoding techniques which are widely used in conventional magnetic resonance imaging. Since the electronic spin state of nitrogen-vacancy (NV)centers is initialized and read out optically, the resolution of current NV magnetometers is limited by optical diffraction. By applying magnetic field gradients, spatial information can be imparted to the phase of NV electron spin precession, and the resolution is inversely proportional to the magnitude of the field gradient. We will discuss methods to make magnetic field gradients of 1 T/cm which can be switched at a rate of 1 MHz in order to achieve 100 nm resolution along two spatial directions. [Preview Abstract] |
Tuesday, March 19, 2013 4:30PM - 4:42PM |
J14.00011: Solid State Hanle Magnetometry Christopher Wolfe, Vidya Bhallamudi, Vivek Amin, Dominic Labanowski, Andrew Berger, Helena Reichlova, David Stroud, Jairo Sinova, Chris Hammel The development of spatially resolved imaging of strongly varying vector magnetic fields is a fundamental challenge that would have scientific and technological implications in fields ranging from materials characterization to the study of magnetic particles in scanned probe techniques and tracking of biological tags. We have extended magnetometry based on the Hanle effect\footnote{A. Kastler, Nucl. Instrum. Methods \textbf{110}, 259 (1973).} to the characterization of vector fields in solid state systems. Local Hanle curves were measured in a GaAs membrane at various positions around a NdFeB micro-magnetic particle using spin-photoluminescence. The spatially varying vector magnetic fields from the micro-magnet cause calculable changes to the shape of the Hanle curve, and by fitting these curves we can extract information about all three components of the field of the micromagnet and infer its properties. I will also discuss the possibility of an all electrical device which could be more easily and broadly utilized. [Preview Abstract] |
Tuesday, March 19, 2013 4:42PM - 4:54PM |
J14.00012: Faraday rotation echo spectroscopy of phase transitions Shaowen Chen, Renbao Liu Faraday rotation is widely used to study magnetic dynamics. We designed a scheme of Faraday rotation echo spectroscopy (FRES) that can be used to study spin noise dynamics in transparent materials by measuring the fluctuation of Faraday rotation angle. The FRES suppresses the static part of the noise and reveal the quantum fluctuations at relatively high temperature, which shares the same idea of the spin echo technique in nuclear magnetic resonance (NMR). We tested our theory on a rare-earth compound LiHoF$_{4}$. The quantum fluctuations obtained by FRES give an enhanced feature at the phase boundary. The FRES can be straightforwardly generalized to more complicated configurations that correspond to more complex dynamical decoupling sequences in NMR and electron spin resonance, which may give us more extensive information on the structural and dynamical properties of magnetic materials. [Preview Abstract] |
Tuesday, March 19, 2013 4:54PM - 5:06PM |
J14.00013: Reading a Magnetic Non-Erasable Magnetic Memory Alan Edelstein, Greg Fischer, Jonathan Petrie, Robert Burke Two major disadvantages of current magnetic memory are that it can be erased by inadvertently applying a magnetic field and the superparamagnetic limit is beginning to make it difficult to increase the density of magnetic recording without further limiting the already too short storage lifetime of seven years. The superparmagnetic limit can be expressed as the requirement to store information for 10 years requires that $KV/k_{B} T > 50$, where $K$ is the crystalline anisotropy, $V$ is the volume of the bit $k_{B}$ is the Boltzman constant and $T$ is the absolute temperature. Alternative methods of information storage, at present, do not have the density of magnetic memory and generally do not store information indefinitely. We have demonstrated a method for reading media in a new magnetic non-erasable memory technology based on regions of high and low magnetic permeability. We have been able to use magnetic tunnel junctions and a probe field to read 10 micron wide lines of a soft magnetic material, permalloy, with a signal to noise ratio of 45 db. [Preview Abstract] |
Tuesday, March 19, 2013 5:06PM - 5:18PM |
J14.00014: Sensing RF and microwave energy with fiber Bragg grating heating via soft ferromagnetic glass-coated microwires M.H. Phan, J. Devkota, H. Srikanth, P. Colosimo, A. Chen The fiber Bragg grating (FBG) is the basis of numerous sensors. For the most part, strain and temperature are the primary environmental parameters that can be detected with FBGs. Other variables can be measured by using a probe design that converts the desired variable to a strain or temperature change. For example, an FBG bonded to the wall of a vacuum chamber might be used to measure pressure if the wall strain vs. pressure calibration were known. We present results from a new type of microwave energy sensor that relies on Joule heating of a soft ferromagnetic glass-coated microwire to change the temperature of an FBG. The microwire absorbs microwave energy and heats up thus raising the temperature of the FBG. Compared to a similar sensor that uses gold to absorb electromagnetic radiation, the microwire yields a sensor with greater sensitivity (10 times at $f=$3.25 GHz) relative to the perturbation of the microwave field. With this newly developed sensor, the best sensitivity to electromagnetic radiation corresponds to AC electric fields that have root mean square (RMS) amplitude of approximately 36 V/m. It is physically very small, can be deployed as a distributed sensor, and often only minimally perturbs the field being measured. [Preview Abstract] |
Tuesday, March 19, 2013 5:18PM - 5:30PM |
J14.00015: Magnetic Field Assisted Assembly: Breaking the 50$\mu $m Barrier Vijay Kasisomayajula, David Cunningham, Anthony Fiory, N.M. Ravindra Magnetic Field Assisted Assembly is used to facilitate heterogeneous device assembly on various substrates. The aim of this work is to illustrate techniques that help assemble devices of dimensions less than 50$\mu $m in any direction onto Silicon/GaAs wafers. Novel methods are developed to produce highly localized magnetic fields using microfabricated solenoids and preconditioned devices whose motion is controlled with nanometer precision. The efficiency of this directed assembly is discussed and comparison is made with existing directed and self assembly techniques. [Preview Abstract] |
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