Bulletin of the American Physical Society
APS March Meeting 2016
Volume 61, Number 2
Monday–Friday, March 14–18, 2016; Baltimore, Maryland
Session B19: Magnetic Devices and Production Level ScalingFocus
|
Hide Abstracts |
Sponsoring Units: GMAG DMP Chair: Joe Davies Room: 318 |
Monday, March 14, 2016 11:15AM - 11:27AM |
B19.00001: Development of 22 T VSM System using Novel Improvements in HTS Conductor Jeremy Good, Darko Bracanovic Current research has identified a need for greater magnetising fields during vibrating sample magnetometer (VSM) measurements and other measurement options. We present here the methodology involved in our development of a VSM system with 22 T superconducting magnet, a unique system and the highest field combined with a VSM anywhere in the world. Recent developments in HTS conductors have allowed greater reliability than previous coils made from YBCO and BISCO and thus facilitate the consistent achievement of higher magnetising fields at the sample with operation at 4.2 K rather than 2.2 K. Cryogenic Ltd wind HTS coils in both solenoid and pancake forms with an emphasis on solenoids, since they have been found to give a more reliable performance with less thermal transfer to the surrounding liquid helium. The 22T VSM system has been developed using 2G YBCO coated and BSSCO tape which exhibit critical currents up to 5 times greater than those seen in YBCO and BISCO at 4.2 K. [Preview Abstract] |
(Author Not Attending)
|
B19.00002: Write operation in MRAM with voltage controlled magnetic anisotropy Kamaram Munira, Sumeet Pandey, Gurtej Sandhu In non-volatile Magnetic RAM, information is saved in the bistable configuration of the free layer in a magnetic tunnel junction (MTJ). New information can be written to the free layer through magnetic induction (Toggle MRAM) or manipulation of magnetization using electric currents (Spin Transfer Torque MRAM or STT-MRAM). Both of the writing methods suffer from a shortcoming in terms of energy efficiency. This limitation on energy performance is brought about by the need for driving relatively large electrical charge currents through the devices for switching. In STT-MRAM, the nonzero voltage drop across the resistive MTJ leads to significant power dissipation. An energy efficient way to write may be with the assistance of voltage controlled magnetic anisotropy (VCMA), where voltage applied across the MTJ creates an electric field that modulates the interfacial anisotropy between the insulator and free layer. However, VCMA cannot switch the free layer completely by 180 degree rotation of magnetization. It can lower the barrier between the two stable configurations or at best, cancel the barrier, allowing 90 degree rotation. A second mechanism, spin torque or magnetic field, is needed to direct the final switching destination. [Preview Abstract] |
Monday, March 14, 2016 11:39AM - 11:51AM |
B19.00003: Tunable Magnetic Resonance via Interlayer Exchange Interaction Yunpeng Chen, Xin Fan, Yunsong Xie, Jeffrey Wilson, Rainee Simons, Sui-Tat Chui, John Xiao Magnetic resonance is a critical property of magnetic materials for the applications in microwave devices and novel spintronics devices. The resonance frequency is commonly controlled with an external magnetic field generated by an energy-inefficient and bulky electromagnet. The search for tuning the resonance frequency without electromagnets has attracted tremendous attention. The voltage control of resonance frequency has been demonstrated in multiferroic heterostructures through magnetoelastic effect. However, the frequency tunable range is limited. We propose a paradigm to tune the magnetic resonance frequency by recognizing the huge interlayer exchange field and the existence of the high-frequency modes in coupled oscillators. We demonstrate the optical mode in exchange coupled magnetic layers which occurred at much higher frequencies than coherent ferromagnetic resonance. We further demonstrated a large resonance frequency tunable range from 11GHz to 21 GHz in a spin valve device by in-situ manipulating of the exchange interaction. The technique developed here is far more efficient than the conventional methods of using electromagnets and multiferroics. This new scheme will have an immediate impact on applications based on magnetic resonance. [Preview Abstract] |
Monday, March 14, 2016 11:51AM - 12:03PM |
B19.00004: Amplification effect of low-field magnetoresistance in silicon dual $p-n$ junctions Dezheng Yang, Tao Wang, Mingsu Si, Fangcong Wang, Shiming Zhou, Desheng Xue Nonmagnetic semiconductors with large magnetoresistance are identified as promising feature for the development of magnetoelectronics. However, to manipulate the magnetoresistance require the magnetic field of several Tesla. In this work, we realized an amplification effect of low-field magnetoresistance based on an elementary electronic building block: dual $p-n$ junction. Analogous to the electrical amplification effect of transistor$ p-n-p_{\thinspace }$junction, where the coupling current between$ p-n$ and $n-p$ junctions is tuned by base current, in a silicon $p+-n-n+$ device we demonstrate that the coupling strength of $p+-n $and $n-n+$ junctions can be tuned by magnetic field. Owing to the amplification effect of magnetic-field-manipulated coupling, at a small magnetic field from 0 to 0.1 T the device is directly switched from conducting state "on" (10000 ohms) to blocking state "off" (5 megohm), yielding an magnetoresistance of 50,000 per cent and magnetic field sensitivity as high as 50 per cent Oe$^{\mathrm{-1}}$. Such a combination of magnetoresistance and high sensitivity not only makes the semiconductor device available in the magnetic field sensing industry, but also permits a new kind of magnetic-field-manipulated semiconductor electronics. [Preview Abstract] |
Monday, March 14, 2016 12:03PM - 12:15PM |
B19.00005: Towards Atomic-Scale Data Storage in Topologically Protected Spin Structures Ralph Skomski, Bala Balamurugan, Priyanka Manchanda, George C Hadjipanayis, D J Sellmyer Model calculations are used to investigate prospects for atomic-scale data storage in topologically protected spin structures. The approach relies exclusively on exchange interactions, as contrasted to storage based on spin-orbit coupling. The latter category includes magnetocrystalline anisotropy, as in present-day ultrahigh-density recording media, and skyrmions involving Dzyaloshinski-Moriya (DM) interactions. Since spin-orbit coupling is a higher-order relativistic correction to the leading electrostatic terms, including exchange, the corresponding bit sizes are limited to about 5 nm at room temperature. Smaller bit sizes are possible at low temperatures, but cooling is not a practicable solution for most data-storage applications. Our mechanism relies on competing but not necessarily frustrated exchange interactions that realize topological protection through spin angles. The approach can also be considered a magnetic analog to cis-trans isomerism in chemistry and polymer science. The corresponding length scale is of the order of 1 nm, corresponding to an areal-density increase by a factor of order 25 compared to date storage based on spin-orbit coupling. Experimental realizations may involve elements in the middle of the iron transition-metal series, such as Cr, Mn, and Fe. - This research is supported by DOE (DE-FG02-04ER46152), ARO (W911NF-10-2-0099), and NCMN. [Preview Abstract] |
(Author Not Attending)
|
B19.00006: Stability of single skyrmionic bits. Olena Vedmedenko, Julian Hagemeister, Niklas Romming, Kirsten von Bergmann, Roland Wiesendanger The switching between topologically distinct skyrmionic and ferromagnetic states has been proposed as a bit operation for information storage. While long lifetimes of the bits are required for data storage devices, the lifetimes of skyrmions have not been addressed so far. Here we show by means of atomistic Monte Carlo simulations that the field-dependent mean lifetimes of the skyrmionic and ferromagnetic states have a high asymmetry with respect to the critical magnetic field, at which these lifetimes are identical. According to our calculations, the main reason for the enhanced stability of skyrmions is a different field dependence of skyrmionic and ferromagnetic activation energies and a lower attempt frequency of skyrmions rather than the height of energy barriers. We use this knowledge to propose a procedure for the determination of effective material parameters and the quantification of the Monte Carlo timescale from the comparison of theoretical and experimental data [1]. [1] Nature Comms. 6, 8455 (2015) [Preview Abstract] |
Monday, March 14, 2016 12:27PM - 12:39PM |
B19.00007: \textbf{Perpendicular reading of single confined magnetic skyrmions} Dax M. Crum, Mohammed Bouhassoune, Juba Bouaziz, Benedikt Schweflinghaus, Stefan Bl{\"u}gel, Samir Lounis We present the first fully self-consistent first-principles investigation of single chiral magnetic skyrmions as entire entities based on density functional theory. The work is tied to skyrmions with sub-5nm diameters embedded within thin ferromagnetic films stabilized through interfacial Dzyaloshinskii-Moriya interactions. We found that the non-collinearity of the magnetic texture inside the skyrmions leads to spin-mixing of the electronic structure, which can be probed as site-dependent tunneling spin-mixing magnetoresistance (TXMR). The conduction inhomogeneity can reach values up to 20{\%} in Pd/Fe/Ir(111) samples [1]. The non-collinear component of the TXMR has been experimentally verified [2], validating our theoretical calculations and showing the capability of the TXMR to resolve complex nanoscale spin-textures. The work is carried out with the newly developed J\"{u}lich relativistic Korringa-Kohn Rostoker Green function method [3]. [1] Crum, D.M. et al. Perpendicular reading of single confined magnetic skyrmions. Nat. Commun. \textbf{6 }8541 (2015). [2] Hanneken, C. et al. Electrical detection of magnetic skyrmions by tunnelling non-collinear magnetoresistance. Nat. Nanotech. doi:10.1038/nnano.2015.218 (2015). [3] Bauer, D.S.G., Schriften des Forschungszentrum, Key Technology \textbf{79} (2014). [Preview Abstract] |
Monday, March 14, 2016 12:39PM - 12:51PM |
B19.00008: Reconfigurable magnetic logic combined with non-volatile memory in silicon. Zhaochu Luo, Xiaozhong Zhang Silicon-based complementary metal-oxide-semiconductor (CMOS) transistors have achieved great success and become the mainstream of integrated logic circuits. However, the traditional pathway to enhance computational performance and decrease cost by continuous miniaturization is approaching its fundamental limits. The recent emergence of magnetic logic devices, especially magnetic-field-based semiconductor logic devices, shows promise for surpassing the development limits of CMOS logic and arouses profound attentions. Based on our Si based magnetoresistance (MR) device [1], we proposed a Si based reconfigurable magnetic logic device by coupling nonlinear transport effect and Hall effect in Si [2], which could do all four basic Boolean logic operations including AND, OR, NOR and NAND combined with non-volatile memory. Further, we developed a Si based current-mode magnetic logic device, which allowed direct communication between different logic devices by current-induced magnetization switch effect without external intermediate magnetic-electric converters. This may result in a memory-logic integrated system leading to a non von Neumann computer. [1] CH Wan, et al, Nature 477, 304, (2011). [2] ZC Luo et al. Adv. Funct. Mater. 25, 158, (2015).. [Preview Abstract] |
Monday, March 14, 2016 12:51PM - 1:03PM |
B19.00009: Toward spin-based Magneto Logic Gate in Graphene Hua Wen, Hanan Dery, Walid Amamou, Tiancong Zhu, Zhisheng Lin, Jing Shi, Igor Zutic, Ilya Krivorotov, Lu Sham, Roland Kawakami Graphene has emerged as a leading candidate for spintronic applications due to its long spin diffusion length at room temperature. A universal magnetologic gate (MLG) based on spin transport in graphene has been recently proposed as the building block of a logic circuit which could replace the current CMOS technology. This MLG has five ferromagnetic electrodes contacting a graphene channel and can be considered as two three-terminal XOR logic gates. Here we demonstrate this XOR logic gate operation in such a device. This was achieved by systematically tuning the injection current bias to balance the spin polarization efficiency of the two inputs, and offset voltage in the detection circuit to obtain binary outputs. The output is a current which corresponds to different logic states: zero current is logic `0', and nonzero current is logic `1'. We find improved performance could be achieved by reducing device size and optimizing the contacts. [Preview Abstract] |
Monday, March 14, 2016 1:03PM - 1:15PM |
B19.00010: Low Drift in Resistance of Plasma Oxidized, Cobalt Confined AlOx Tunnel Barriers Z. S. Barcikowski, Y. Hong, J. M. Pomeroy Co/AlOx/Co tunnel junctions show \textless 15{\%} drift in resistance measured over the first three months. This long term stability is achieved using plasma oxidation and sandwiching the AlOx tunnel barrier between cobalt layers. Plasma oxidation of aluminum, when compared to thermal oxidation, has been shown to produce a more homogeneous and stoichiometric oxide. The confinement of the oxide between Co layers, which have higher oxide enthalpies of formation, is thought to provide a barrier against oxygen diffusion. Junction resistance and current-voltage (I-V) measurements are taken over a period of approximately 9 months. Barrier width (s) and asymmetric barrier heights ($\varphi_{1}$, $\varphi_{2})$ are extracted using Simmons/Chow transport model. Bottom barrier height ($\varphi_{2})$ and barrier width (s) show near constant values in contrast to a rise in top barrier height ($\varphi_{1})$ in time. [Preview Abstract] |
Monday, March 14, 2016 1:15PM - 1:27PM |
B19.00011: A Study of Morphology and Magnetic Properties of Doped Barium Ferrite Films Formed by Aerosol Deposition Scooter Johnson, Christopher Gonzalez, Zachary Robinson, David Ellsworth, Mingzhong Wu Aerosol deposition is a room-temperature thick film deposition technique that produces polycrystalline films that have $>$ 95\% of theoretical density and are up to several hundred microns thick. In addition to depositing films at room temperature another distinct advantage of aerosol deposition is the ability to produce films with the same resulting stoichiometry as the starting material. For this work, we deposited a proprietary doped barium ferrite (BaFe$_{12}$O$_{19}$) film from powder produced by {\em Temex Ceramics}. This material is designed for microwave absorption near 18 GHz via ferromagnetic resonance. We compare the structural and magnetic properties of the as-deposited film, bulk material, and starting powder. For this purpose, we employed scanning electron microscopy, x-ray photoemission spectroscopy, x-ray diffraction, vibrating sample magnetometry, and broad-band ferromagnetic resonance characterization techniques. [Preview Abstract] |
Monday, March 14, 2016 1:27PM - 1:39PM |
B19.00012: Large-area patterned substrates for micromagnetic actuation of superparamagnetic microbeads Minae Ouk, Geoffrey S.D. Beach Superparamagnetic microbeads(SBs) have been used to capture and manipulate biological entities in a fluid environment. Chip-based magnetic actuation provides a means to transport SBs in lab-on-a-chip technologies. This is accomplished using the stray field from patterned magnetic microstructures [1], or domain walls in magnetic nanowires [2]. Recently many studies have focused on the submicron-size antidot array of magnetic materials because non-magnetic holes affect the micromagnetic properties. Here, we use photolithographic pattering to create periodic anti-dot arrays in Co thin films, show the transport of SBs across large distance by a rotating field. We describe the dynamics of bead motion, highlighting the key factors to control bead transport. We show there is a critical threshold for both in-plane and out-of-plane components that must be exceeded for bead motion to occur. The threshold values are different depending on direction, which allows for directionally-anisotropic transport across the chip surface. Hence the periodic magnetically-patterned substrates can be used to digitally separate magnetic beads and augment microfluidic actuation for long distance transport.[1]B. Yellen, et al., Lab Chip, 7, 1681 (2007) [2]E. Rapoport and G. S. D. Beach, APL 100, 082401 (2012) [Preview Abstract] |
Monday, March 14, 2016 1:39PM - 1:51PM |
B19.00013: Measurement of Nanoparticle Magnetic Hyperthermia Using Fluorescent Microthermal Imaging Xiaowan Zheng, Edward Van Keuren Nanoparticle magnetic hyperthermia uses the application of an AC magnetic field to ferromagnetic nanoparticles to elevate the temperature of cancer cells. The principle of hyperthermia as a true cell-specific therapy is that tumor cells are more sensitive to high temperature, so it is of great importance to control the locality and magnitude of the temperature differences. One technique to measure temperature variations on microscopic length scales is fluorescent microthermal imaging (FMI). Since it is the local temperature that is measured in FMI, effects such as heating due to nearby field coils can be accounted for. A dye, the rare earth chelate europium thenoyltrifluoroacetonate (Eu:TTA), with a strong temperature-dependent fluorescence emission has been incorporated into magnetic nanoparticles dispersed in a polymer films. FMI experiments were carried out on these samples under an applied high frequency magnetic field. Preliminary results show that FMI is a promising technique for characterizing the local generation of heat in nanoparticle magnetic hyperthermia. [Preview Abstract] |
Monday, March 14, 2016 1:51PM - 2:03PM |
B19.00014: Optimization of magnetic refrigerators by tuning the heat transfer medium and operating conditions. Mohammadreza Ghahremani, Amir Aslani, Lawrence Bennett, Edward Della Torre A new reciprocating Active Magnetic Regenerator (AMR) experimental device has been designed, built and tested to evaluate the effect of the system's parameters on a reciprocating Active Magnetic Regenerator (AMR) near room temperature. Gadolinium turnings were used as the refrigerant, silicon oil as the heat transfer medium, and a magnetic field of 1.3 T was cycled. This study focuses on the methodology of single stage AMR operation conditions to get a higher temperature span near room temperature. Herein, the main objective is not to report the absolute maximum attainable temperature span seen in an AMR system, but rather to find the system's optimal operating conditions to reach that maximum span. The results of this work show that there is an optimal operating frequency, heat transfer fluid flow rate, flow duration, and displaced volume ratio in an AMR system. It is expected that such optimization and the results provided herein will permit the future design and development of more efficient room-temperature magnetic refrigeration systems. [Preview Abstract] |
Monday, March 14, 2016 2:03PM - 2:15PM |
B19.00015: Impact of DC Joule anneal treatment on the high-frequency magnetoimpedance response of Fe-rich FeCo ribbons with varying glass former content Tatiana Eggers, Alex Leary, Michael McHenry, Ivan Skorvanek, Hariharan Srikanth, Manh-Huong Phan The Magnetoimpedance (MI) effect in 2 mm wide (Fe$_{\mathrm{65}}$Co$_{\mathrm{35}})_{\mathrm{83.5-x}}$B$_{\mathrm{13}}$Nb$_{\mathrm{x}}$Si$_{\mathrm{2}}$Cu$_{\mathrm{1.5}}$ rapidly quenched ribbons with varying glass former content(x $=$ 0 and x $=$ 4) has been studied in the frequency range of 1-1000 MHz. Two measurement techniques were used: auto-balancing bridge method in the frequency range of 1-110 MHz and transmission line technique for 20-1000 MHz. The impact of DC Joule heating treatments of varying current amplitude and annealing time on the MI effect of the amorphous ribbons was evaluated by examining the field and frequency dependence on the resistive and reactive components of the MI. To interpret the MI behavior, the domain structure of the ribbons in their as-quenched state and after heating treatment was imaged by magneto-optical Kerr effect microscopy. A significant improvement in the MI response from the as-quenched state was found for both compositions of ribbon with a 3 hour-500 mA Joule anneal treatment. The improvement is attributed to the development of a low anisotropy domain structure longitudinally and at an oblique angle between the longitudinal and transverse directions for the 0{\%} and 4{\%} Nb content, respectively. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700