Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session N55: 2D Materials: MagnetismFocus
|
Hide Abstracts |
Sponsoring Units: GMAG Chair: Yaohua Liu, Oak Ridge National Lab Room: Room 305 |
Wednesday, March 8, 2023 11:30AM - 12:06PM |
N55.00001: Investigate 2D antiferromagnetism in van der Waals materials by nonlinear optics Invited Speaker: Zhuoliang Ni Detecting the spin structures in antiferromagnetic materials is normally considered hard, especially for two-dimensional materials where samples are usually thin and small. Here, I will show that the optical second-harmonic generation (SHG) is an ideal tool for detecting various types of two-dimensional antiferromagnetism, including the non-centrosymmetric Neel type and centrosymmetric Zigzag type. The polarization-dependent measurement reveals the orientations of spins and an SHG confocal microscope further generates the spin orientation distribution across the sample in the diffraction limit. I will show how we use SHG to investigate three different 2D antiferromagnets, the Heisenberg-type MnPS3, the XY-type MnPSe3, and the Ising-type FePS3. |
Wednesday, March 8, 2023 12:06PM - 12:18PM |
N55.00002: Novel ways to tune magnetism in metal thiophosphates MPX3 Rabindra Basnet, Kamila K Kotur, Milosz Rybak, Cory Stephenson, Samuel Bishop, Carmine Autieri, Magdalena Birowska, Jin Hu Recent discoveries in two-dimensional magnetism have intensively motivated the search of new van der Waals magnetic materials and further engineer their magnetic properties for potential use in spintronics applications. Tunable magnetism has been widely studied in antiferromagnetic metal thiophosphates MPX3. Substitution of metal ions M has been adopted as a common technique to manipulate their magnetism. Here, we present other approaches to tune magnetism in MPX3: chalcogen X substitution and lithium intercalation. Our studies reveal the effective control of magnetic exchanges and anisotropies upon chalcogen substitution. In addition, we found the signature of ferrimagnetism up on Li intercalation in van der Waals-type MPX3, which provides alternative route to achieve various magnetic phases in MPX3 that are not accessible through metal substitution. |
Wednesday, March 8, 2023 12:18PM - 12:30PM |
N55.00003: Magnetic property of directly exfoliated and dispersed Fe3GeTe2 and Fe5GeTe2 in pure water hyunjong Lim, Hyobin Ahn FexGeTe2 (X=3, 5), two-dimensional(2D) ferromagnetic materials, have attracted many researchers due to its strong Ising-type anisotropy and relatively high curie temperature. However, methods for preparing large-area FexGeTe2 film is at a starting point. Selection of precursors and optimization of synthesis condition make overall progress and design of experiment complicated, as they are composed of three elements. Here, we exfoliate Fe3GeTe2 and Fe5GeTe2 via wet exfoliation in pure water by sonication with heating and fabricate cm-scale film through filtration. The coercivity of FeXGeTe2 film increases dramatically, in the case of Fe3GeTe2, from 20mT which is coercivity of bulk crystal, to 650mT. The coercivity of FeXGeTe2 is reported to increase as their thickness decreases. When they become thinner, they behave as single-domain magnet, so that their coercivity increases. Even when they are stacked in film form, edge-functionalization disturbs interactions between nano-magnets, situation doesn’t change. Our work suggests a simple and facile method to fabricate large-area film of FexGeTe2 with improved magnetic properties. |
Wednesday, March 8, 2023 12:30PM - 12:42PM |
N55.00004: Tuning the magnetic anisotropy, Curie temperature, and Dzyaloshinskii-Moriya interaction in the FeCl2 monolayer Udo Schwingenschlogl, Paresh C Rout, Shubham Tyagi The emergence of magnetic ordering in two-dimensional materials offers unique opportunities for developing novel spintronics devices. However, these materials suffer from low magnetic critical temperature, in-plane anisotropy, and low magnetic anisotropy energy. We will discuss a strategy for the ferromagnetic FeCl2 monolayer (based on first-principles and Monte Carlo simulations) to enhance the Curie temperature to above room temperature and enhance the magnetic anisotropy energy by nearly three orders of magnitude, which is essential for sustaining long-range magnetic ordering. In addition, we find a non-polar (1T) to polar (1H) structural phase transition and induced Dzyaloshinskii-Moriya interaction, which is crucial for generating chiral magnetic structures such as skyrmions. |
Wednesday, March 8, 2023 12:42PM - 12:54PM |
N55.00005: Strain engineering of impurity-induced magnetism in doped graphene nanostructures: A first-principles study Juan Hernandez-Tecorralco, Lilia Meza-Montes, Romeo De Coss Modulation of magnetism in low-dimensional systems could enable the development of novel devices in emerging quantum technologies. Mechanical strain has been shown to be an effective magnetic tuning technique in different low-dimensional materials. Regarding to magnetic systems, we are interested in the induced magnetism in graphene through the incorporation of impurities with only s and p electrons. In this work, we present a systematic study of the effect of uniaxial strain on the phosphorus-induced magnetism in graphene and its nanoribbons, performed by means of first-principles calculations. In order to analyze the dimensionality effects, we studied the monolayer and nanoribbons of different widths and edges (armchair and zig-zag), in the range from 0 to 10% of deformation. We find that for the monolayer, the uniaxial strain slightly modulates the magnetic moment, while for nanoribbons a magnetic phase transition is induced, but critical strain depends on nanoribbon width. |
Wednesday, March 8, 2023 12:54PM - 1:06PM |
N55.00006: Twist-angle dependent all van der Waals spin-valve operations Keun-Hong Min, Dukhyun Lee, Jonghwa Eom, Jun-Sung Kim, Suyong Jung Two-dimensional (2D) magnetic materials and their heterostructures with atomically clean van der Waals (vdW) interfaces provide an excellent experimental platform to realize novel spintronic device operations. In addition, twistronics, whose primary device attribute is associated with the alignment angles of the single-crystalline layered materials, has been an active research field for the past several years. However, experimental realizations of twistronics employing the versatility of twist angles with 2D magnetic materials have not been demonstrated yet. Here we present the twist-angle dependent spin-valve operations with all vdW-assembled vertical magnetic tunnel junctions (MTJs) made of 2D metallic ferromagnet Fe3GeTe2 (FGT) and tunnel insulator hexagonal boron nitride (hBN). We have found that vertical spin-dependent charge transport behaviors of the all-vdW-assembled vertical MTJs are highly sensitive to the twist angles of the 2D metallic ferromagnets and the relative spin configurations of the FGT electrodes. The tunneling magnetoresistance ratio of the FGT-hBN-FGT spin valves is measured to be as high as ~ 480% for the device with a 2° twist angle and continually decreases to ~ 100% and lower as the misalignment angle increases. These unprecedented twist-angle dependent spin-valve operations provide a new control knob for low-dimensional spintronic applications. |
Wednesday, March 8, 2023 1:06PM - 1:18PM |
N55.00007: Voltage Controlled Interlayer Magnetic Coupling in a 2D Magnet Yasen Hou, Yingying Wu, Hang Chi, Jagadeesh S Moodera Electric voltage controlled magnetism in spintronic devices provides unique opportunity to surpass the speed, efficiency, functionality and integration density of current electronic devices, which is one of the most versatile and efficient means to control the magnetism and enable new capabilities leveraging atomically thin two-dimensional (2D) magnet-based devices. Here, we demonstrate tunability of the interlayer magnetic coupling of even-layer van der Waals magnetic semiconductor CrSBr by electric gating in a graphite/h-BN/CrSBr/bottom electrodes vertical heterostructure. In evenlayer CrSBr, electric gating can switch the interlayer coupling between ferromagnetic and antiferromagnetic states. Hysteresis loops for the transition between these two magnetic states are observed to depend on gating voltage up to 140 K. Our work demonstrates voltage tunability of magnetism in 2D magnets, which is key to enabling multiple functionality and develop low-power spintronic, magnonic and valleytronic devices capable of on-chip communication. |
Wednesday, March 8, 2023 1:18PM - 1:30PM |
N55.00008: Scanning tunnelling microscopy of a two-dimensional magnetic material Olivia Armitage, Akhil Rajan, Sebastian Buchberger, Philip King, Peter Wahl Understanding the properties of 2D materials as well as their interactions with each other is important for building heterostructures with tuneable properties. Here, we study the interactions of a 2D magnetic monolayer of CrSe2 with a graphite substrate by low-temperature Scanning Tunnelling Microscopy (STM) and Spectroscopy. CrSe2 is a Transition Metal Dichalcogenide, a layered van der Waals material which can exist in either the 1T or distorted 1T’’ structure, characterised by the tetramerization of the Cr atoms. Antiferromagnetic order becomes more favourable than ferromagnetic as the lattice constant and Cr-Cr distance decreases, but whilst the 1T form is metallic, the 1T’’ has a small band gap. Islands of monolayer CrSe2 are grown on graphite by Molecular Beam Epitaxy. I will discuss topographic and spectroscopic imaging of the morphology and electronic structure of films which exhibit the 1T’’ structure. We observe additional modulations in the CrSe2 due to a charge-density wave with a periodicity consistent with a Moiré supercell with the graphite surface at 19° relative rotation. From quasiparticle interference imaging we find a linear band dispersion qualitatively similar to the Dirac cones of graphene. We model the heterostructure by Density Functional Theory (DFT) calculations and compare the electronic structure obtained from DFT with the dispersion observed in quasiparticle interference. |
Wednesday, March 8, 2023 1:30PM - 1:42PM |
N55.00009: Restrictive thermodynamic stability and intrinsic ferromagnetism in MA2N4 and Janus VSiGeN4 monolayers Dibyendu Dey, Avijeet Ray, Liping Yu A handful of predicted magnetic two-dimensional (2D) materials in the MA2Z4 family (M = transition metals, A = Si, Ge, and Z = N, P, As) were predicted to be dynamically stable, but none of them has been synthesized to date. In this work, from the first-principles thermodynamic stability analysis, we demonstrate that only the nitrides are thermodynamically stable under N-rich conditions. In the group of 2D magnetic nitrides, VSi2N4 has been found to be the most stable monolayer, from which two Janus ferromagnetic monolayers, namely, VSiGeN4 and VSiSnN4, have been designed. They are both dynamically and thermally stable, but only the former is thermodynamically stable. Intriguingly, these two semiconducting Janus monolayers show weak in-plane anisotropy compared to the VSi2N4 monolayer. A large valley polarization can be induced in VSiGeN4 and VSiSnN4 monolayers through the valley splitting of the bottom conduction band. The magnetic properties of these 2D ternary layered vanadium-based Janus semiconductors make them emerging candidates for spintronics and optoelectronics applications. |
Wednesday, March 8, 2023 1:42PM - 1:54PM |
N55.00010: Voltage Control of the Magnetic Anisotropy in Fe2.7GeTe2/In2Se3 van der Waals Heterostructures Jaeun Eom, Jin Hong Lee, INHAK LEE, Jung Yun Kee, Minhyun Cho, Hoyoung Suh, Yu Liu, Hye Jung Chang, Cedomir Petrovic, Hyejin Ryu, Chaun jang, Young Duck Kim, Dohun Kim, Se Young Park, Jun Woo Choi The discovery of van der Waals (vdW) materials has introduced unique opportunities to design unexplored heterostructures by mechanical exfoliation and transfer of various vdW materials. In this work, we fabricate a heterostructure device consisting of vdW ferromagnetic Fe2.7GeTe2 (FGT) and vdW piezoelectric/ferroelectric α-In2Se3 (IS), and observe the FGT magnetic properties as it is voltage-gated by the IS layer. Our magneto-optical Kerr effect (MOKE) measurement shows that the gate voltage can manipulate the magnetic coercivity of FGT, confirming the magnetoelectric interaction between the FGT and IS. The change in FGT magnetic coercivity and anisotropy is attributed to the voltage-controlled strain on the FGT by our Raman spectroscopy and density functional theory (DFT) calculation. Our results pave a way for low-power voltage-driven vdW spintronic devices. |
Wednesday, March 8, 2023 1:54PM - 2:06PM |
N55.00011: Strain effect on Magneto-crystalline anisotropy of atomically thin Fe3GeTe2 GyeongHye Kim, Qurat ul Ain, Sonny H. Rhim Two-dimensional magnetism [1, 2] has attracted huge attentions, where Fe3GeTe2 (FGT) has Curie temperature larger than 130 K [3]. Here, magneto-crystalline anisotropy (MCA) of mono- and bilayer FGT are studied with density functional theory. Perpendicular MCA, the preference for perpendicular magnetism, is advantageous for high bit density, thermal stability, and lower switching current [4]. Under strain (–5%≤η≤+5%), EMCA of monolayer FGT varies from 0.85 to 4.15 meV/f.u.; that of bilayer FGT does from –0.56 to 4.82 meV/f.u. For both cases, under compressive (tensile) strain EMCA decrease (changes little). From band analysis, without strain, (m=±1|LZ|m=±1) contributes to EMCA > 0. However, when η=–5%, due to upward band shift, m=±1 states become unoccupied: (m=0|LX|m=±1) emerges giving EMCA < 0. For monolayer, EMCA > 0 contribution wins EMCA < 0 for all η. On the other hand, for bilayer, EMCA > 0 contribution wins EMCA < 0 for all η except η≤–4%. |
Wednesday, March 8, 2023 2:06PM - 2:18PM |
N55.00012: Hard magnetic response of exfoliated van der Waals Ferromagnet Fe5-xGeTe2, and coexistence between merons and skyrmions Alex J Moon, Yue Li, Brian Casas, Luis Balicas Magnetic two-dimensional materials show very intriguing properties and have recently emerged as a very promising new area in condensed matter physics with significant potential for applications in magnonics, low power spintronics quantum computing, and optical communication. However, Curie temperature (Tc) of many of the known 2D ferromagnets are well below room temperature. For example, Cr2GeTe6 (Tc ~ 60 K), CrI3 (Tc ~ 45 K), and Fe3GeTe2 (Tc ~ 220 K). Intriguely, Fe5GeTe2 displays a Tc as high as 330 K, which means that it has a great potential for applications. Motivated by the Hall response of exfoliated Fe3GeTe2 that is dominated by the anomalous Hall, we measured large magnetic coercivity and found the change in direction of hard magnet in nanoflakes of Fe5-xGeTe2. The size of the hysteresis depends on the crystal thickness with magnetic coercive field (Hcr) increasing with decreasing the layer thickness. Furthermore, we will present our result showing the magnetic domain of Fe5-xGeTe2 measured via Lorentz Transmission Electron Microscopy (LTEM) measurement with the range of temperature 100 K~300 K. Evidences for coexistence between merons and skrymions, and how they change will be shown with various temperatures. |
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