Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session C38: Spin Dynamics and ExcitationsFocus Session Live
|
Hide Abstracts |
Sponsoring Units: GMAG DMP FIAP Chair: Shawn Pollard , University of Memphis |
Monday, March 15, 2021 3:00PM - 3:12PM Live |
C38.00001: AMPLITUDE REPRESENTATION OF THE LANDAU-LIFSHITZ EQUATION Gang Li, Chen Sun, Valery L Pokrovsky We use a classical representation for the Landau-Lifshitz equation, the energy spectrum of magnons is studied. Also, we apply this theory to get the exact phase diagram for different values of thickness d and magnetic field H and relaxation time of condensed magnons. |
Monday, March 15, 2021 3:12PM - 3:24PM Live |
C38.00002: Equations of motions for spin-1 magnets — a u(3) formalism, suitable to investigate dynamical and thermodynamical properties Kimberly Remund, Rico Pohle, Yutaka Akagi, Judit Romhanyi, Nicholas Shannon Spin-1 magnets include dipolar and quadrupolar moments on a single site, which allow for novel, unconventional phases, such as spin nematics [Blume69]. |
Monday, March 15, 2021 3:24PM - 3:36PM Live |
C38.00003: Correlated Magnetic Properties in Ultra-low Damping
Ferromagnetic and Heavy Metal Bilayers David Lujan, Aidan J Lee, Tsun Chun Chang, Timothy N Nunley, Kemal Sobotkiewich, Shang-Fan Lee, Fengyuan Yang, Xiaoqin (Elaine) Li For both spin torque oscillators and switching devices using heavy metal/ferromagnetic (HM/FM) structures, low-damping ferromagnets (FM) are highly desirable. Using momentum-resolved Brillouin light scattering, we investigate a series of epitaxially grown Pt (3 nm)/CoxFe1-x bilayers that exhibit the lowest damping in metallic FMs. Taking into account saturation magnetization and lattice constant from other measurements, we extract several critical parameters including the volumetric and interfacial Dzyaloshinskii-Moriya interaction constants, exchange stiffness, exchange length, effective damping, spin mixing conductance as a function of FM layer thickness. |
Monday, March 15, 2021 3:36PM - 3:48PM Live |
C38.00004: Spin Echo Simulations and Supervised Machine Learning Charles Snider, Stephen Carr, Dmitri Feldman, Chandrasekhar Ramanathan, Brad Bradley Marston, Vesna Mitrovic
|
Monday, March 15, 2021 3:48PM - 4:00PM Live |
C38.00005: Magnetization dynamics of room-temperature vdWs magnet Fe5GeTe2 Laith Alahmed, Bhuwan Nepal, Juan Macy, Kaya Wei, Wenkai Zheng, Arjun Sapkota, Alessandro Mazza, Matthew Brahlek, Wencan Jin, Shulei Zhang, Claudia K.A. Mewes, Luis Balicas, Tim Mewes, Peng Li Two-dimensional (2D) van der Waals (vdWs) materials have gathered a lot of attention in recent years due to their potential applications for spintronic devices. A big setback with these 2D crystals is their low Curie temperatures Tc < 300 K. As a promising room-temperature vdWs magnet, Fe5GeTe2 has gained a lot of attention because of its high Tc of about 270 K[1]. In our work, we synthesized bulk Fe5GeTe2 crystals and studied the magnetic properties by temperature-dependent vibrating sample magnetometry (VSM) and ferromagnetic resonance (FMR) techniques. VSM measurements of the bulk Fe5GeTe2 sample reveal an in-plane anisotropy with a Curie temperature of 320 K. Thermal capacity measurements show that the sample experiences phase transitions which can be correlated with the changes in magnetism. From the FMR measurements, the gyromagnetic ratio shows a disparity along the in-plane and out-of-plane directions, indicative of orbital momentum contribution. Moreover, the low intrinsic damping indicates a weak intervalley scattering in Fe5GeTe2, making it an interesting platform to study spin dynamics. |
Monday, March 15, 2021 4:00PM - 4:12PM Live |
C38.00006: Spin-orbit exciton in a honeycomb lattice magnet CoTiO3: Revealing a link between magnetism in d- and f-electron systems Bo Yuan, Matthew Brandon Stone, Guo-Jiun Shu, Fangchang Chou, Xin Rao, James P.I. Clancy, Young-June Kim We present inelastic neutron scattering study of the spin-orbit (SO) exciton in a single crystal sample of CoTiO3 as a function of temperature. CoTiO3 is a honeycomb magnet with dominant XY-type magnetic interaction and an A-type antiferromagnetic order below TN ≈38 K. We observed strong temperature dependence of the SO exciton going from the ordered to paramagnetic phase: a significant softening and an increase in its bandwidth at T>TN, as well as appearance of a second mode at intermediate temperatures below TN. Such an unusual temperature dependence observed in this material suggests that its ground states (an Seff = 1/2 doublet) and excited states multiplets are strongly coupled and therefore cannot be treated independently, as often done in a pseudospin model. Our observations can be explained by a multilevel theory within random phase approximation that explicitly takes into account both the ground and excited multiplets. The success of our theory, originally developed for the rare-earth systems, highlights the similarity between magnetic excitations in f- and d-electron systems with strong spin-orbit coupling. |
Monday, March 15, 2021 4:12PM - 4:24PM Live |
C38.00007: Nonlocal Gilbert damping and magnetic interactions in noncollinear magnetic nanostructures from first principles Sascha Brinker, Manuel dos Santos Dias, Samir Lounis Damping is essential to the magnetization dynamics underpinning the performance of any type of magnetic device. Utilizing a first-principles description of the spin dynamics of noncollinear magnetic nanostructures based on linear-response time-dependent density functional theory [1], we demonstrate that the Gilbert damping and gyromagnetic tensors can be expressed in terms of couplings, chiral or not, of the magnetic moments. We illustrate the theory considering magnetic adatoms, dimers and trimers, both within a generalized Alexander-Anderson model and using real magnetic atoms on Au(111) together with magnetic constraints [2]. These properties are related to the filling of the magnetic orbitals of the clusters, to their hybridization with the surface electrons, and to the role played by spin-orbit coupling. We put forward a generalized Landau-Lifshitz-Gilbert equation accounting for the dependence of damping on the underlying magnetic structure and address the dynamics of different magnetic ground states. |
Monday, March 15, 2021 4:24PM - 4:36PM Live |
C38.00008: Ultrafast Spin Dynamics in the Chiral Helimagnet Cr1/3NbS2 Hengzhou Liu, Minh Tuan Trinh, Ellie M Clements, Ling Li, David George Mandrus, Hariharan Srikanth, Manh-Huong Phan, Denis Karaiskaj The control of charge and spin degree of freedom of materials by ultrafast optical pulse enables novel sensing technology, quantum computing, terahertz emission, ultrafast optical switching, and ultrafast data storage. Chiral helimagnetic materials have recently attracted much attention for spintronic applications owing to their long-range helical magnetic order, topological spin textures, and potential for hosting skyrmions. Here, we present an ultrafast spin dynamics study in single crystals of chiral helimagnet Cr1/3NbS2 using the time-resolved magneto-optical Kerr effect technique. At low temperature and low external magnetic field, Cr1/3NbS2 exhibits a chiral helical magnetic phase with long-range helical spin order but contains a zero net magnetic moment. Due to the high uniaxial anisotropy of the crystal, a linearly polarized femtosecond laser pulse can magnetize the material in tens of ps, which brings the system into the chiral conical phase at zero-field and tilted chiral soliton lattice phase at a higher external magnetic field. In addition, we have found that the magnetic field-dependence of spin precession frequency in this helimagnet does not obey Landau-Lifshitz-Gilbert formalism as applied for ferromagnetic materials in general. |
Monday, March 15, 2021 4:36PM - 4:48PM Live |
C38.00009: Spin excitations in the multiferroic skyrmion host GaV4S8 Ganesh Pokharel, Hasitha Suriya Arachchige, Georg Ehlers, Seunghwan Do, Matthew Brandon Stone, Mark D Lumsden, Hao Zhang, Yiming Qiu, Randy Fishman, Stephen D Wilson, David George Mandrus, Andrew Christianson In GaV4S8, the interplay of spin, charge, and orbital degrees of freedom results in a complex phase diagram that includes cycloidal, ferromagnetic, ferroelectric, orbitally ordered, and skyrmion phases. To provide insight into the interactions rendering this complex phase diagram, the spin excitations in GaV4S8 are studied using inelastic neutron scattering measurements of polycrystalline and single crystalline samples. The characteristic features of spin waves propagating along the high symmetry directions (110) and (001) are described. A Heisenberg spin model with competing symmetric and asymmetric exchange (DM) interactions explain the experimental data. Simulation shows ferromagnetic inter-tetrahedral couplings with J= -0.70(3) meV. The modeling further indicates that the DM interactions are around 15% of the nearest neighbor exchange interactions. The finding of the interaction parameters in GaV4S8 provides an important information about the magnetic ground state in GaV4S8. |
Monday, March 15, 2021 4:48PM - 5:00PM Live |
C38.00010: Structure change across the Morin transition temperature of single crystal α-Fe2O3 Jiaming He, Suyin Wang, Yu-sheng Chen, Jianshi Zhou Alpha-ferric oxide (α-Fe2O3) has been the subject of extensive studies aiming to determine the relationship between spontaneous magnetic moments and structure. Below its Néel temperature TN = 948 K, the iron magnetic moments are antiferromagnetically ordered, previous studies by neutron diffraction across the Morin temperature (TM=263 K) have found the Fe moments lie in the rhombohedral (111) plane above the TM and form the canted spin structure that gives rise to weak ferromagnetism (FM), upon cooling through TM, the easy axis of spins rotates to Hexagonal c axis and magnetization drops. The weak FM is believed to be caused by Dzyaloshinskii-Moriya interaction (DMI). However, S-state for Fe3+ makes the spin-orbit couple and therefore DMI negligible. Here, we synthesized high-quality single crystal α-Fe2O3 and used synchrotron X-Ray diffraction to explore likely subtle change of local structure, which might be driving force for the change of easy axis and spin canting across TM. We found the unit cell size and Fe-O bond length decreases upon cooling, the Fe-O octahedral become less distorted, the long axis of the octahedral shifted towards Hexagonal c axis. |
Monday, March 15, 2021 5:00PM - 5:12PM Live |
C38.00011: Micromagnetic modeling of skyrmion and domain wall dynamics in Pt/TmIG systems Denis Pelekhov, Jacob B. Freyermuth, Camelia Selcu, Adam S Ahmed, Nuria Bagues Salguero, Jason Guo, Aidan J Lee, Igor Lyalin, Brendan McCullian, Binbin Wang, Po Kuan Wu, P Chris Hammel, Roland Kawakami, David W McComb, Fengyuan Yang, Mohit Randeria We present investigation of skyrmion and domain wall formation and dynamics in Pt/Tm3Fe5O12(TmIG) bilayers. In the system domain wall and skyrmion motion is driven by Spin Hall Effect (SHE) induced by the electric current flowing in the Pt layer. Micromagnetic modeling is done using the magnetic parameters determined specifically for the Pt/TmIG bilayers grown at the Ohio State University. The parameters used in micromagentic modeling were experimentally measured on the grown films using a broad range of experimental techniques including, but not limited to, Ferromagnetic Resonance, SQUID Magnetometry and topological Hall measurements. The modeling is done using both the commercially available and the custom developed software. The objective of the investigation is to determine the path to achieving high velocities of skyrmion motion. We compare our modeling results with the results of Magnetic Force Microscopy and Magneto-Optical Kerr Effect microscopy measurements. |
Monday, March 15, 2021 5:12PM - 5:48PM Live |
C38.00012: Unconventional dynamics of ferrimagnets in the vicinity of compensation points Invited Speaker: Se Kwon Kim Ferrimagnets have recently emerged as versatile platforms for spintronics owing to their unique tunability of material parameters. In particular, they offer the independent control of the spin density and the magnetization, which are impossible to achieve in more conventional magnets such as ferromagnets and antiferromagnets and thereby offer unprecedented opportunity to discover novel spin physics and realize highly tunable spintronic devices. In this talk, we will discuss the recent theoretical progress on the ensuing novel dynamics of ferrimagnets. The topics will include the dynamics of topological solitons such as domain walls [1,2], skyrmions [3,4], and vortices [5] within the framework of the generalized Landau-Lifshitz-Gilbert-like equations for ferrimagnets. Also, the novel properties of spin waves in ferrimagnets based on two distinct handedness will be discussed [6,7]. The talk will be concluded by providing a future outlook on ferrimagnetic spintronics and by discussing some fundamental questions that we are facing to understand the non-equilibrium properties of ferrimagnets [8]. |
Monday, March 15, 2021 5:48PM - 6:00PM Live |
C38.00013: Characterization of the Dynamics of FeRh using Time-Domain Thermoreflectance (TDTR) Renee Harton, Nadya Mason, David G. Cahill FeRh exhibits an antiferromagnetic(AF)/ferromagnetic (FM) phase transition. This change in magnetic order is accompanied by an increase in lattice parameter. Using Time-Domain Thermoreflectance (TDTR), a pump probe technique used to determine the thermoreflectance (TR) of samples, we studied the dynamics of FeRh. For these measurements TDTR was conducted at various temperatures within the transition region. At each base temperature, we used small temperature excursions to determine the dynamics near each temperature. We found that for time delays shorter than the thermally-driven transition mechanism, the TR of the AF and FM phases have opposing signs. Using this feature, we observed a pronounced response within the AF phase for time delays less than 1 ps. These results suggest that shortly following excitation, the electrons, magnons and phonons exhibit significant non-equilibrium behavior, while equilibrium is achieved on the picosecond timescale. These findings also suggest that the dynamics of the FeRh sample occur on both the subpicosecond timecale and the picosecond timescale. |
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. |
© 2025 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