Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session B54: Skyrmion Based DevicesFocus Recordings Available
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Sponsoring Units: GMAG Chair: Jean Incorvia, University of Texas Room: McCormick Place W-476 |
Monday, March 14, 2022 11:30AM - 11:42AM |
B54.00001: Ferromagnetic Domain Wall Qubit Architecture. Dalton R Jones We define a novel qubit architecture based on the dynamics of a one-dimensional domain wall within a spin wave cavity. An advantage of such a system is the ability to operate at high temperature as compared to the state of the art superconducting qubits, while offering a directly analogous form of the Hamiltonian and environmental interactions. |
Monday, March 14, 2022 11:42AM - 11:54AM |
B54.00002: Skyrmion Qubits Christina Psaroudaki
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Monday, March 14, 2022 11:54AM - 12:06PM |
B54.00003: Skyrmion Based Physical Reservoir Computing Md Mahadi Rajib, Walid Al Misba, Md Fahim F Chowdhury, Muhammad Sabbir Alam, Jayasimha Atulasimha Physical reservoir computing (PRC) is one of the leading unconventional computing paradigms which is capable of performing recognition and classification tasks by exploiting nonlinear dynamics of reservoir blocks [1, 2]. We demonstrate the use of thin films hosting several skyrmions, particularly one, two, three, four and nine skyrmions, as a block for implementing reservoir computing. Our concept utilizes the breathing of skyrmions in response to an applied electric field, which are coupled through dipole interaction and spin waves. This nonlinear [3] and coupled magnetization dynamics is exploited to perform temporal pattern recognition. Two performance metrics, namely short-term memory and parity check capacity were studied to demonstrate the potential of high performance of skyrmion based PRC. Furthermore, our study demonstrates that nonlinear magnetization dynamics and interaction through spin waves and dipole interaction affect memory and parity check capacity and explain the role of physical interactions in this dynamical system in its ability to perform reservoir computing. |
Monday, March 14, 2022 12:06PM - 12:42PM |
B54.00004: Gate-Controlled Skyrmion Chirality Invited Speaker: Helene Bea Magnetic skyrmions are localized chiral spin textures, which offer great promise to store and process information at the nanoscale. In the presence of asymmetric exchange interactions, their chirality, which governs their dynamics, is generally considered as an intrinsic parameter set by the sample composition. In this work, we demonstrate that this key parameter can be controlled by a gate voltage. We observed that the current-induced skyrmion motion can be reversed by the application of a gate voltage. This local and dynamical switching of the skyrmion chirality is due to a sign inversion of the interfacial Dzyaloshinskii-Moriya interaction that we attribute to ionic migration of oxygen under gate voltage. Micromagnetic simulations show that the chirality reversal is a continuous transformation, in which the skyrmion is conserved. This gate-controlled chirality provides a local and dynamical degree of freedom, yielding new functionalities to skyrmion-based logic devices. |
Monday, March 14, 2022 12:42PM - 12:54PM |
B54.00005: Dipolarly coupled nanomagnets as hardware emulators of neurons for brain-like computing systems Ankit Shukla, Siyuan Qian, Shaloo Rakheja Magnetic materials and their heterostructures can host a range of nonlinear dynamics including phase transitions and criticality, self-oscillations, synchronization, stochastic resonance, and chaos, which form the basis of many brain algorithms. Recent theory has demonstrated current-induced spike-like dynamics in (synthetic) antiferromagnets and easy-plane ferromagnets. In this research, we present the theory of non-linear hysteretic dynamics emergent in dipolarly coupled nanomagnets and show that such systems can be used as hardware emulators of neurons. Numerical models are developed to (i) explore the regimes of coherent and incoherent oscillations and (ii) estimate the performance metrics (energy, latency, area) of dipolar neurons as a function of geometry and material properties of the nanomagnets. The effect of thermal noise on the linewidth of the output signal and its spectral purity is also quantified. Finally, we show that local-level connectivity between dipolar neurons could be established at the thermodynamic limits solely using magnetic dipolar coupling, or spin diffusion. Our results will guide experimental studies of energy- and area-efficient magnetic devices for brain-like computing. |
Monday, March 14, 2022 12:54PM - 1:06PM |
B54.00006: Skyrmion Stochastic Dynamics for Novel Computing Architectures Zulfidin Khodzhaev, Emrah Turgut, Mario F Borunda Using the instabilities and stochastic behavior of skyrmions, new computing architectures, e.g., neuromorphic, probabilistic and reservoir computing can be achieved [1-3]. The major aspect of this computation is understanding synaptic response and having a constant uncorrelated signal [2]. In this study, the stochastic property in a shuffling chamber is investigated using micromagnetic simulations. In particular, the temperature response to the number of skyrmions in a chamber is analyzed. Our study explored skyrmion dynamics under different geometries, constant temperatures, grains and different currents to get a stochastic skyrmion motion. Then, two locations, along the path of the skyrmions were chosen for local laser spot heating, keeping grain, current density and geometry constant. Finally, for constant temperatures, synaptic response is shown. This study will provide guidelines for the creation of a better probabilistic computing device and artificial synapse. |
Monday, March 14, 2022 1:06PM - 1:18PM |
B54.00007: Thermally driven magnon valves TmIG/Au/TmIG with perpendicular magnetic anisotropy Gilvania L Da Silva Vilela, Eduardo Santos, José E Abrao, Alexandre Ricalde, Sergio M Rezende, Antônio Azevedo, Jagadeesh S Moodera The use of magnons to carry, transport, and process information could lead to faster processing of information free of Joule heating and, with a phase extra degree of freedom since magnons are quanta of spin waves. Like the conventional spin valves, magnon valves are trilayers used to control the flow of magnon currents with the potential to become the building block of magnonics devices. In this work, we fabricated magnon valves TmIG/Au/TmIG with perpendicular magnetic anisotropy (PMA). The PMA is an advantageous feature that allows a higher density of data storage in recording media and facilitates the control of the magnetic state of a thin film via spin-transfer torque and magnon-transfer torque. For exciting magnon currents through the valve, a longitudinal thermal gradient was applied to the trilayer as a spin Seebeck voltage was detected through the inverse spin Hall effect in a platinum electrode film deposited on the top of the structure. The PMA magnon valves showed three distinct levels for controlling the flow of magnons. These results shed light on the use of spin waves in computing devices. |
Monday, March 14, 2022 1:18PM - 1:30PM |
B54.00008: Chirality Memory Stored in Magnetic Domain Walls in the Ferromagnetic State of MnP Nan Jiang, Yoshinori Onose, Yoichi Nii, Hiroki Arisawa, Eiji Saitoh, Jun-ichiro Ohe Chirality in a helimagnetic structure is determined by the sense of magnetic moment rotation. We found that the chiral information did not disappear even after the phase transition to the high-temperature ferromagnetic phase in a helimagnet MnP. The 2nd harmonic resistivity ρ2f , which reflects the breaking down of mirror symmetry, was found to be almost unchanged after heating the sample above the ferromagnetic transition temperature and cooling it back to the helimagnetic state. The application of a magnetic field along the easy axis in the ferromagnetic state quenched the chirality-induced ρ2f . This indicates that the chirality memory effect originated from the ferromagnetic domain walls. |
Monday, March 14, 2022 1:30PM - 1:42PM |
B54.00009: Ultrathin ferrimagnetic GdFeCo films with very low damping Lakhan Bainsla, Ahmad Awad, Akash Kumar, Mohammad Zahedinejad, Nilamani Behera, Himanshu Fulara, Roman Khymyn, Afshin Houshang, Johan Åkerman Spin-Hall nano oscillators (SHNOs) [1] have recently emerged as an alternative for microwave signal generation and bio-inspired oscillatory computing [2]. Due to their ultrafast magnetization dynamics with a ferromagnet-like spin-orbit-torque (SOT) behavior, there is a lot of interest in compensated ferrimagnets. For use in SHNOs, it is however important to ensure that such films retain their ferrimagnetic behavior also in ultrathin films. In this work, ferrimagnetic Gdx(FeCo)1-x thin films were grown on high resistance (HR) Si (100) substrates, and their magneto-dynamics was studied using ferromagnetic resonance measurements at room temperature. By tuning the stoichiometry, a nearly compensated behavior is for the first time demonstrated in 2 nm thin films. Values for the effective magnetization and effective Gilbert damping constant (α) of 0.02 Tesla and 0.0078 comparable to the lowest values obtained in thick films. In search of high-frequency auto-oscillations in SHNOs, constrictions with 50-300 nm widths were also prepared using Gdx(FeCo)1-x (2-10nm)/Pt(5nm) based stacks and Brillouin Light Scattering show SOT controllable ferromagnetic modes in these devices. |
Monday, March 14, 2022 1:42PM - 1:54PM |
B54.00010: Weak ferromagnetic interaction between magnetic layers studied by X-ray ferromagnetic resonance Chanyong Hwang, Changsoo Kim, Zi Q. Qiu X-ray Magnetic Circular Dichroism(XMCD) provides useful information about a spin angular momentum of a magnetic element. X-ray ferromagnetic resonance(XFMR) can measure a precessional motion of magnetization of each element when it is combined with XMCD. When the dynamics of multilayered thin film composed of different magnetic elements is measured using XFMR, precessional motions of each layers can be observed separately. We inserted a normal metal (Ti) between the thick magnetic layer (Py) and the thin magnetic layer (CoFeB) to evaluate an interaction between the magnetic layers. The interaction between the two layers was observed until the thickness of Ti reached 10 nm. We simulated the ferromagnetic resonances of these two layers using two Landau-Lifshitz-Gilbert equations to determine the type and strength of the interaction. A ferromagnetic coupling between the two magnetic layers was observed, and the smallest interaction amplitude was estimated to be ~1.2 μJ/m2 with Ti (10 nm) insertion layer. |
Monday, March 14, 2022 1:54PM - 2:06PM |
B54.00011: Antiferromagnetic Bloch line driven by spin current - an analog of a fluxon in a long Josephson junction Roman Ovcharov, Roman Khymyn, Boris Ivanov, Johan Akerman Antiferromagnets (AFMs) are promising for future high-frequency field-free spintronic applications [1-4]. Self-localized spin structures can substantially enrich this scope and endow new functionalities to AFM-based devices [5]. A domain wall (DW) is a topological soliton that bridges a connection between two ground states, similar to a link in a Josephson junction (JJ) between two superconductors. |
Monday, March 14, 2022 2:06PM - 2:18PM |
B54.00012: Modeling High-Frequency Electromagnetics in Tunneling Magnetoresistive Sensors* Andrew Maicke, Jean Anne C Incorvia, Ali Yilmaz, Calvin Chan As operating frequencies of modern magnetic devices increase, effects of high-frequency (HF) electromagnetic fields on device behavior must be analyzed. Common micromagnetic (μM) software solve the Landau-Lifshitz-Gilbert (LLG) equation for the material magnetization under a magnetostatic approximation and can miss effects such as excited eddy currents which increasingly contribute to magnetization dynamics at HF [1]. To demonstrate the necessity of coupling the full dynamic Maxwell (M) and LLG equations, we radiate a sequence of waves up to 3 GHz from stripline antennas onto a tunneling magnetoresistive sensor and show the sensor resistance diverges from predictions of a LLG equation solver as wave frequency increases. We then formulate a hybrid M-LLG system of equations, modeling LLG terms using finite-differences (FD) and the M contribution to the demagnetization field using the FD time-domain method. We use the μM standard problems [2] to validate the proposed M-LLG solver and test its accuracy and computational costs. Finally, we discuss parallel performance of the solver on a supercomputing cluster. |
Monday, March 14, 2022 2:18PM - 2:30PM |
B54.00013: Hydrogen irradiation-induced magnetic phase transition modulation in FeRh films Sehwan Song, Chang-woo Cho, Jiwoong Kim, Jisung Lee, Dooyong Lee, Doukyun Kim, Hyegyeong Kim, Haeyong Kang, Chul-Hong Park, Chanyong Hwang, Jun Kue Park, Sungkyun Park FeRh shows metamagnetic first-order phase transition from antiferromagnetic to ferromagnetic above 370 K. Also, it accompanies a volume expansion of about 1% and variation of electrical resistivity due to the increasing density-of-state at the Fermi level. To utilize phase transition characteristics for spintronics device applications, the transition temperature should be adjustable. Multiple methods such as doping, inducing interfacial strain, and forming various defect states have been attempted to modify the phase transition characteristics. |
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