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 LL04: V: Magnetic NanostructuresFocus
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Sponsoring Units: GMAG Chair: Jack Gartside, Imperial College London Room: Virtual Room 4 |
Tuesday, March 21, 2023 5:00AM - 5:36AM |
LL04.00001: Observation of Spin Swapping in an Antiferromagnet Invited Speaker: Weiwei Lin The transport of spin angular momentum of electrons is fundamental in condensed matter physics. Spin current phenomena, such as spin Hall and spin Seebeck effects, have been known to be essential in spintronics in recent decades. In this talk, we show the experimental evidence for swapping of spin currents, the interchange of directions of spin (magnon) flow and spin index, in a canted antiferromagnetic insulator LaFeO3 [1]. This effect enables the electrical readout of room-temperature magnetization switching in antiferromagnetic insulators, paving the way for the challenging antiferromagnetic spintronics. |
Tuesday, March 21, 2023 5:36AM - 5:48AM |
LL04.00002: Two-dimensional spin-spiral materials with spins rotating on an inclined plane: PtCl2, PdCl2 and PdBr2 Yan-Fang Zhang, Jie Zhang, Jinbo Pan, Sokrates T Pantelides, Shixuan Du Interest in spin-spiral materials has been on the rise due to inherent magnetoelectric coupling with potential applications in spintronic devices. Two-dimensional PtCl2, PdCl2 and PdBr2 in the 1T phase have been theoretically predicted to be antiferromagnetic semiconductors [1]. However, there are no experimental investigations on these three materials yet. Here, by performing density-functional-theory calculations, we revisit these materials, considering non-collinear magnetic order. It is found that spin spirals are the lowest-energy magnetic ordering for all three materials in the 1T phase at the LDA+U level. Spins rotate in an inclined plane, which is quasi-parallel to the metal-halogen bond direction. The spin-spiral ground state and an indirect bandgap are robust for different U values. The spin-spiral induced polarizations of all three materials are comparable with that of monolayer FeOCl, which was predicted recently [2]. These results enrich the two-dimensional families of spin-spiral systems. |
Tuesday, March 21, 2023 5:48AM - 6:00AM |
LL04.00003: Determination of perpendicular magnetic anisotropy in magnetic heterostructures: DFT-based spin-orbit torque method Yu-Hui Tang, Bao-Huei Huang, Yi-Feng Lai In order to increase the storage capacity of magnetoresistive random-access memories (MRAMs), the reduction of size of memory cell requires the enhancement of the magnetic anisotropy to meet the criterion of thermal stability. The recently discovered perpendicular magnetic anisotropy (PMA) at the ferromagnetic metal/oxide and ferromagnetic metal/heavy metal interfaces plays a crucial role in MRAM applications. However, both first-principles calculated total energy and fitted experimental data remain difficult to quantitatively evaluate the magnetic anisotropy energy (MAE), especially in magnetic heterostructures with complex interfaces between multi-layers. |
Tuesday, March 21, 2023 6:00AM - 6:12AM |
LL04.00004: Flexomagnetism of thin Cr2O3 films Oleksandr V Pylypovskyi, Pavlo Makushko, Tobias Kosub, Natascha Hedrich, JIang Li, Alexej Pashkin, Stanislav Avdoshenko, Rene Hübner, Fabian Ganss, Daniel Wolf, Axel Lubk, Maciej Oskar Liedke, Maik Butterling, Andreas Wagner, Kai Wagner, Brendan Shields, Paul Lehmann, Ihor Veremchuk, Jürgen Fassbender, Patrick Maletinsky, Denys Makarov Cr2O3 is the only known uniaxial antiferromagnetic material that is also magnetoelectric at room temperature. This renders Cr2O3 a technologically relevant playground for the realisation of different device ideas for prospective antiferromagnetic spintronics. We discovered the presence of flexomagnetic effects in Cr2O3, which come about due to the impact of a strain gradient on the thermodynamic properties, namely on the Neel temperature. By combining magnetotransport and Nitrogen Vacancy magnetometry characterizations, we experimentally determine the presence of the gradient of the Neel temperature in a 50-nm-thick Cr2O3 thin film and quantify that the magnetic moment, generated by this new effect, can be as high as 15 μB/nm2. Furthermore, due to good oxide-oxide heteroepitaxy and respective compressive strain, the Neel temperature in Cr2O3 thin films can be enhanced persistently up to 100 °C, which is 60 °C higher than the bulk transition temperature. The emergent flexomagnetism-driven ferromagnetic order parameter in antiferromagnetic thin films offers more flexibility in the design of spintronic and magnonic devices and can be of relevance for other antiferromagnetic materials. |
Tuesday, March 21, 2023 6:12AM - 6:24AM |
LL04.00005: Strain-Induced Magnetism in Defective Graphene Md Z Hossain Vacancy defects are known to induce magnetization in graphene. However, understanding the effects of defect-defect interaction on magnetization under applied strain remains elusive. This talk will present the effects of symmetry-breaking strain on magnetization in multidefect graphene. We used the density functional theory simulation under the generalized gradient approximation for the exchange-correlation energy to investigate the magnetic consequence of strain applied along different directions relative to the defect pair. Our results show that the spin magnetic moment increases with increasing strain. Decomposition of the total magnetic effects into the individual effects of the orbitals reveals that the $p_z$ orbital dominates the change in the total magnetic moment, while the net change of the local moment in $p_x$ and $p_y$ orbitals are the same but with opposite signs. Nonetheless, for a pair of monovacancies, the strain does not affect the spin magnetic moment when the inter-defect distance reaches a critical value. However, the magnetic moment increases with increasing strain for a longer inter-defect distance, and the combined effects can be well-approximated as a linear superposition of their individual effects. Additionally, if the defects are magnetically isolated, there exists a critical strain whereat each of the defects experiences a second-order Jahn–Teller reconstruction (JTRR) that switches the orientation of the defect and alters the magnitude of the magnetic moment. These results are expected to shed new light on controlling the magnetic behavior of a single or multi-defect system as a function of the separation distance and the intensity of mechanical strain. |
Tuesday, March 21, 2023 6:24AM - 6:36AM |
LL04.00006: The Effect of Hf Doping on Piezomagnetic Properties of FeCo for Magnetoelectric Heterostructure Devices Peter Finkel Artificial magnetoelectrics, built on the combination of ferromagnetic magnetostrictive materials structurally coupled to piezoelectric and ferroelectric materials, display the ability to control magnetic properties of the ferromagnet with electric voltage across the piezo/ferroelectric layer. The best performance requires the implementation of soft magnetic materials with large magnetostriction and large voltage-induced strain in the piezo/ferroelectric layer. Processing requirements for device fabrication often complicate the realization of these combined qualities as inherent stresses from the deposition technique are often detrimental to the magnetoelectric functionality. Solutions to these problems are rarely reported though alloying of FeCo and subsequent metalloid substitutions such as (Fe0.5Co0.5)1-xCx, and (Fe0.5Co0.5)1-xBx, have proven successful in reducing the coercive field while retaining high magnetostriction and piezomagnetic properties. |
Tuesday, March 21, 2023 6:36AM - 6:48AM |
LL04.00007: Spatially reconfigurable topological textures in freestanding antiferromagnetic nanomembranes Hariom Jani, Jack Harrison, Sonu Hooda, Saurav Prakash, Junxiong Hu, Proloy Nandi, zhiyang zeng, Jheng-Cyuan Lin, Ganesh Ji Omar, Jörg Raabe, Simone Finizio, Aaron Thean, Ariando Ariando, Paolo G Radaelli Antiferromagnets hosting real-space topological spin textures are promising platforms to explore novel fundamental and functional spintronics phenomena.To date, they have only been fabricated epitaxially on specific symmetry-matched crystalline substrates, which preserve their intrinsic magneto-crystalline order. This curtails integration of topological antiferromagnets with dissimilar 2D/3D supports, markedly restricting the scope of fundamental and applied investigations. Here, we circumvent this limitation by designing detachable crystalline antiferromagnetic nanomembranes that can be transferred onto other desirable supports after growth. We develop transmission-based antiferromagnetic vector-mapping to show that these nanomembranes also harbour rich topological phenomenology at room temperature. Moreover, we exploit their extreme flexibility to demonstrate 3D antiferromagnetic state reconfiguration, which is driven locally via flexure-based strains. Integration of such freestanding antiferromagnetic layers onto targeted supports could enable new explorations into magnetoelastic and geometry-controlled spin texture design, quasi-static and dynamical antiferromagnetic studies, and development of unconventional computing platforms. |
Tuesday, March 21, 2023 6:48AM - 7:00AM |
LL04.00008: Labyrinth and Stripe Domains in Bismuth doped YIG thin films: Experiment and Theory Bellave S Shivaram, Victoria R Knight, Gia-Wei Chern, Ziyuan Wang We report magneto-optical measurements of stripe and labyrinthine domains in Bi doped Yitrium Iron Garnet single crystal films with perpendicular magnetocrystalline anisotropy. High resolution images are captured with a digital camera thus enabling comprehensive post acquisition analysis of the domain patterns and their movement with changing DC applied fields. Measurements made with the field at different orientations with respect to the plane of the film will be reported. The use of pattern recognition software reveals key signatures of the domain patterns that contribute to the bulk of the changes observed in the characteristic magnetization hysteresis loops. These key features are also captured by a model Hamiltonian with exchange, anisotropy and long-range dipole-dipole interaction terms which we solve numerically using the package OOMMF. . |
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