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 K56: Kagome Materials |
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Sponsoring Units: GMAG Chair: Keith Taddei, Oak Ridge National Lab Room: Room 304 |
Tuesday, March 7, 2023 3:00PM - 3:12PM |
K56.00001: Chemical control of magnetism in the Kagome metal CoSn1-xInx: Magnetic order from nonmagnetic substitutions Brian C Sales, William R Meier, David S Parker, Li Yin, Jiaqiang Yan, Andrew F May, Stuart Calder, Adam A Aczel, Qiang Zhang, Haoxiang Li, Turgut Yilmaz, Elio Vescovo, Hu Miao, Duncan H Moseley, Raphael P Hermann, Michael A McGuire The Pauli paramagnet, CoSn consists of Kagome layers of Co, which generates flat bands and a |
Tuesday, March 7, 2023 3:12PM - 3:24PM |
K56.00002: Noncoplanar magnetic state and scalar spin chirality driven large anomalous Hall effects in electron doped Mn3Sn Ajaya Kumar Nayak, Charanpreet Singh, Sk Jamaluddin, Ashis Nandy, Masashi Tokunaga, Maxim Avdeev The discovery of a large anomalous Hall effect (AHE) in non-collinear antiferromagnet Mn3Sn begins a new era of antiferromagnetic (AFM) spintronics [Nakatsuji et al., Nature 527, 212 (2015]. Mn3Sn exhibits an in-plane triangular 120 degree AFM ordering owing to the geometrical frustration in the kagome lattice. In this work, we present a combined theoretical and experimental investigation to show how suitable electron doping in the Mn3Sn can drastically change the in-plane AFM structure to a tunable non-coplanar magnetic state. We demonstrate that the higher-order exchange interaction in the magnetic Hamiltonian drives the planar magnetic state to the non-coplanar one. We also find a large scalar spin chirality (SSC)-induced topological AHE, whose size is closely correlated with the system's degree of noncoplanarity. Additionally, a unique simultaneous manipulation of the dual order in the system is demonstrated, where the Hall signal due to in-plane AFM order can be switched independently without perturbing the SSC-induced signal. The current work provides a new avenue for investigating unique quantum phenomena in triangular AFM materials where higher order magnetic interactions play a vital role. |
Tuesday, March 7, 2023 3:24PM - 3:36PM |
K56.00003: Impact of Dzyaloshinskii-Moriya and anisotropic exchange interactions on the spin configurations and excitations in the cubic kagome antiferromagnets Mn3X and Mn3AB Jason McCoombs We perform a symmetry analysis of the ABC-stacked kagome planes of Mn atoms common to the L12 Mn3X and antiperovskite Mn3AB alloys. In addition to the single-ion-anisotropy and Kitaev-type anisotropic exchange known to stabilize the 120-degree spin structures in these materials, our analysis results in a staggered Dzyaloshinskii-Moriya interaction and further gamma-type anisotropic exchange between nearest-neighbor spins. The presence of these new terms is shown not to affect the energetics of the 120-degree ground-states which explains their absence in prior minimal magnetic models. We go on to show, however, that the influence of these terms is swithced on when spin-wave excitations are considered, resulting in reduced symmetry and magnon band gaps. We highlight these effects by calculating inelastic neutron scattering cross-sections to illustrate possible experimental routes for probing the existence and relative strengths of these cloaked interactions. |
Tuesday, March 7, 2023 3:36PM - 3:48PM |
K56.00004: Theory of transverse magnetization in spin-orbit coupled antiferromagnets Taekoo Oh Some antiferromagnets under a magnetic field develop magnetization perpendicular to the field as well as more conventional ones parallel to the field. So far, the transverse magnetization (TM) has been attributed to either spin canting effect or the presence of cluster magnetic multipolar ordering. However, a general theory of TM based on microscopic understanding is still missing. Here, we construct a general microscopic theory of TM in antiferromagnets with cluster magnetic multipolar ordering by considering classical spin Hamiltonians with spin anisotropy that arises from the spin-orbit coupling. First, from general symmetry analysis, we show that TM can appear only when all crystalline symmetries are broken other than the antiunitary mirror, antiunitary two-fold rotation, and inversion symmetries. Moreover, by analyzing spin Hamiltonians, we show that TM always appears when the degenerate ground state manifold of the spin Hamiltonian is discrete, as long as it is not prohibited by symmetry. On the other hand, when the degenerate ground state manifold is continuous, TM generally does not appear except when the magnetic field direction and the spin configuration satisfy specific geometric conditions under single-ion anisotropy. Finally, we show that TM can induce anomalous planar Hall Effect, a unique transport phenomenon that can be used to probe multipolar antiferromagnetic structures. We believe that our theory provides a useful guideline for understanding the anomalous magnetic responses of the antiferromagnets with complex magnetic structures. |
Tuesday, March 7, 2023 3:48PM - 4:00PM |
K56.00005: Electronic and Magnetic Properties of 2D Breathing-Kagomé Magnets Tharindu Warnakulasooriya Fernando, Xiaowei Zhang, Ting Cao Kagomé materials have received significant interest recently since they can host flat bands due to their lattice configurations. This makes them a platform for the study of the interplay between geometry, topology, electronic correlations, and magnetism. In this talk, we use density functional theory calculations to investigate the 2D Kagomé magnetic semiconductor Nb3I8. Our calculations demonstrate flat bands that are consistent with experimental ARPES measurements [1]. We further show that the magnetic exchange interactions in this material allow for novel and tunable magnetic phases. |
Tuesday, March 7, 2023 4:00PM - 4:12PM |
K56.00006: Interplay between magnetism and electronic structure in the quasi-kagome magnet HoAgGe Hari Bhandari, Resham Regmi, Madhav P Ghimire, Igor I Mazin, Nirmal J Ghimire Kagome lattice magnets are an intresting class of materials that inherently allow a unique platform for the interplay between magnetism and electronic topology as they are one of the highly frustrated magnetic systems and also allow the simultaneous existence of topological flat bands and Dirac points. A kagome lattice consists of corner sharing equilateral triangles arranged forming a hexagonal pattern. In the RAgGe (R = rare earth element) compounds crystallizing in the ZrNiAl-type structure, the R atoms form the equilateral triangles similar to that in the kagome lattice, but these triangles are slightly rotated not making the prefect hexagonal ordering. Such a quasi-kagome lattice of the 4f electrons provides a platform for intresting physics, which was recently demonstrated by the discovery of the elusive spin-ice in HoAgGe. The spin-ice rules in this compound (one-in-two-out or two-in-one-out) are obeyed with increasing applied field along the b-axis, which leads to metamagnetic transitions in Ms/3 increments ( where Ms is the saturated magnetization). Here, we present the magnetotransport properties in the different magnetic states stablized the magnetic field in this material. We have found a significant effect of the magnetic structure on the Hall conductivity. We will discuss the Hall conductivity as a function of magnetic field and temperature providing the evidence of the interplay between the intriguing magnetism and the electronic structure in this compound. |
Tuesday, March 7, 2023 4:12PM - 4:24PM |
K56.00007: Electrochemical Control of Magnetism on the Breathing Kagome Network of LixScMo3O8 Kira Wyckoff, Linus Kautzsch, Jonas Kaufman, Stephen D Wilson, Anton Van der Ven, Ram Seshadri Controlling properties within a given functional inorganic material structure type is often accomplished through tuning the electronic occupation, which is in turn dictated by the elemental composition, that is usually decided at the material preparation. We show here that we can employ electrochemical control of lithium content, with associated electronic occupancy control, to vary the magnetic properties of a material where a kagome-derived network of Mo3 triangles carry the spin. In this case, Li is electrochemically inserted into LiScMo3O8, a layered material containing a breathing Mo kagome network. We demonstrate insertion of up to two additional Li into LiScMo3O8, approaching Li3ScMo3O8. Li2ScMo3O8 prepared by electrochemical lithiation is compared to the quantum spin liquid candidate material Li2ScMo3O8 prepared through high-temperature solid-state methods, that has a slightly different structural stacking sequence but a similar kagome-derived network. Magnetic measurements are supported by first-principles calculations, showing that electrons remain localized on the Mo clusters throughout the doping series. As x is varied in LixScMo3O8, the measurements and calculations reveal the evolution from a diamagnetic band insulator at x = 1 to a geometrically frustrated magnet at x = 2, back to a diamagnetic insulator at x = 3. |
Tuesday, March 7, 2023 4:24PM - 4:36PM |
K56.00008: Weakly canted antiferromagnetic order in the distorted kagome lattice: Y2Co3 Yunshu Shi, Huibo Cao, Eun Sang Choi, Neil Harrison, Kasey P Devlin, David S Parker, Yin Li, Jingtai Zhao, Susan M Kauzlarich, Peter Klavins, Valentin Taufour We report on the physical properties of a new antiferromagnet Y2Co3 with distorted kagome lattice. We developed a solution-growth based method to synthesize single crystals of Y2Co3 and characterize its magnetic properties, magnetic phase diagram and magnetic structure. We find that Y2Co3 crystallizes in the La2Ni3-type orthorhombic structure with space group Cmce (No.64), with Co forming distorted kagome layers. Y2Co3 orders antiferromagnetically below TN = 252 K. Magnetization measurements reveal that the moments are primarily aligned along the b axis with evidence for some canting. Single crystal neutron diffraction was used to determine the magnetic structure. It confirms the major magnetic component along the b axis but did not observe the canted magnetic component. We discuss the magnetic and structural behaviors in the distorted kagome lattice and the discrepancy between the bulk measurement and neutron diffraction. |
Tuesday, March 7, 2023 4:36PM - 4:48PM |
K56.00009: Resolving the importance of soft mode excitations on the magnetocaloric effect of frustrated Heisenberg magnets in the liquid-He regime EliseAnne C Koskelo, Paromita Mukherjee, Cheng Liu, Alice C Sackville Hamilton, Harapan S Ong, Mike E Zhitomirsky, Claudio Castelnovo, Sian E Dutton Frustrated magnetic oxides are ideal candidates for magnetocaloric refrigeration due to suppressed ordering temperatures. Materials design has focused on tuning magnetic moments, their interactions, and density, but less so on the frustrating lattice. Prior theoretical work predicted an enhancement of the magnetocaloric cooling rate via a macroscopic number of soft mode excitations that arise due to the classical ground state degeneracy. The number of these modes is directly determined by the geometry of the frustrating lattice. Among corner-sharing geometries, the pyrochlore has 3/2 as many modes as the garnet and kagome lattices, while the number of soft modes for the edge-sharing fcc is sub-extensive. Here, we study the role of soft modes in the magnetocaloric effect of four large-spin Gd3+ (S=7/2) Heisenberg antiferromagnets on a kagome, garnet, pyrochlore, and fcc lattice. Measurements of the magnetic entropy change at fields up to 9 T provide qualitative agreement with the theoretical prediction. We find that the superexchange dominates the observed magnetocaloric effect in the liquid-He regime (2-20 K) rather than the soft mode excitations. Our results may inform future materials design in terms of dimensionality, degree of magnetic frustration, and lattice geometry. |
Tuesday, March 7, 2023 4:48PM - 5:00PM |
K56.00010: Half-Magnetization Plateau in a Spin-3/2 Kagome-Strip-Lattice Na2Co3(VO4)2(OH)2 Yiqing Hao, Megan Smart, Joseph Kolis, Liurukara D Sanjeewa, Huibo Cao Geometric frustration and quantum fluctuations are key ingredients to new types of complex quantum magnetic ground states. In some non-trivial quantum states, a specific spin arrangement can be stabilized in a range of external magnetic fields, manifesting as a plateau in the M-H curve, known as the magnetization plateau. Magnetization plateaus are previously found in honeycomb and kagome lattices, linking to many-body quantum effects and spin anisotropies. Here, we report a half-magnetization plateau in the newly synthesized kagome-strip-lattice (KSL) material, Na2Co3(VO4)2(OH)2. KSL is a one-dimensional variety of a kagome lattice, which consists of alternating hexagonal and triangular motifs along one direction, the strip-direction. Our susceptibility measurements reveal the half-magnetization plateau by applying the field perpendicular to the strip-direction. To understand the origin of the magnetization plateau, we used single crystal neutron diffraction to investigate the evolution of magnetic structures with field. At zero field, the magnetic ground state is a non-collinear antiferromagnetic order with reduced ordered-magnetic moments on all Co sites. By increasing the magnetic field, only 1/3 of the Co sites are flipped to ferromagnetic order, while 2/3 of the Co sites remain small to zero ordered-magnetic moments despite the strong magnetic field. Such robustness in reducing ordered-magnetic moments shows intense magnetic frustration and strong quantum fluctuations in this KSL material. Furthermore, assisted with the local magnetic susceptibility method using polarized neutrons and theoretical simulation, I will discuss the mechanism of forming the resultant ground state and the half-magnetization plateau. |
Tuesday, March 7, 2023 5:00PM - 5:12PM |
K56.00011: Frustration, dipolar, and quadrupolar physics on the square lattice oxyhalides DyOX (X=Cl,Br,I) David T Brooks, Xiaojian Bai, Stuart Calder, Ovidiu O Garlea, Martin P Mourigal “Rare-earth ions are an important ingredient in frustrated magnetism due to their propensity for anisotropic magnetization distributions. Due to this and their crystal field splitting allowing for an effective spin-½ degrees of freedom, they are commonly investigated in the search for exotic magnetic phases of matter. The Dysprosium Oxy-halides (DyOX, X=Cl,Br,I) have come under recent investigation as both layered Van der Waals materials [1] and a realization of a frustrated J1-J2 model (this work), with interplanar spacing being a function of the halide’s ionic radius. This, paired with Dysprosium’s high magnetic moment and single-ion quadrupolar behavior, leads DyOX to be an exciting platform to study specific aspects of quantum magnetism that are generally difficult to probe. This talk will present several forms of data: neutron diffraction and scattering, thermomagnetic measurements, and simulation results to elucidate their magnetic properties. The results systematically show two ordering transitions, yet dramatically different magnetic structures across the family of compounds. We will compare these compounds’ magnetic properties, as well as the origin of this unique behavior.” |
Tuesday, March 7, 2023 5:12PM - 5:24PM |
K56.00012: Thermodynamics of the Breathing Kagome Antiferromagnet Nd3BWO9 Jakob Nagl, Daniel Flavian Blasco, Shohei Hayashida, Zewu Yan, Severian Gvasaliya, Andrey Zheludev The recently discovered family of rare-earth based kagome lattice antiferromagnets RE3BWO9 [1] with breathing anisotropy has been garnering much attention in the field of quantum magnetism. Here we present a thermodynamic study on single crystals of the spin-orbit entangled jeff = 1/2 Kramers system Nd3BWO9 [2]. In spite of the significant frustration, we identify a transition to long range order at TN = 0.3 K. Measurements of the specific heat, magnetization and magnetocaloric effect are carried out to map the entire H-T phase diagram and investigate effects of anisotropy. In this process, we uncover a series of intriguing ordered phases in applied magnetic fields. Our findings provide key insights relevant to any further study of this series of rare-earth based quantum magnets. |
Tuesday, March 7, 2023 5:24PM - 5:36PM |
K56.00013: Generalized Kibble-Zurek mechanism for annealing dynamics of pyrochlore spin ice Zhijie Fan, Adolfo del Campo, Gia-Wei Chern Spin ices are novel magnetic systems that are characterized by a disordered, yet highly correlated, low-temperature phase and quasi-particles which carry a net magnetic charge. These emergent magnetic monopoles are fractionalized excitations, which can be viewed as the high-dimensional analogue of kinks in the 1D ferromagnetic Ising model. Indeed, spin-ice systems share many unusual features with the Ising chain, such as the lack of a finite-temperature phase transition and an emergent critical point at the zero-temperature limit. Moreover, the critical behaviors of spin ices and Ising chain are peculiar in that the correlation length follows an exponential divergence as T goes to zero, instead of the power-law behavior as in conventional continuous phase transition. Here we study the nonequilibrium dynamics of kagome and pyrochlore spin ices under a slow cooling protocol and investigate the dependence of residual monopole densities on the annealing rate. We show that the kagome ice does not exhibit scaling behavior in the slow cooling limit. On the other hand, thanks to the topological nature of monopoles in pyrochlore spin ice, its annealing dynamics is well described by a generalized Kibble-Zurek mechanism. |
Tuesday, March 7, 2023 5:36PM - 5:48PM |
K56.00014: Pressure and magnetic field-induced phase transitions in rare-earth-based kagome magnets Alessia Provino, Noah Kramer, Christopher Hanley, Pietro Manfrinetti, Arjun K Pathak Materials crystallizing with a Kagome lattice, whose atoms are arranged into layered sets of overlapping corner-sharing triangles, show breaking of time-reversal symmetry and potentially can, therefore, host novel correlated topological states. Among the several systems, the RMn6Sn6 (R = rare earth) compounds have shown several interesting physical properties, including Chern topological magnetism, and anomalous Hall effect [Phy. Rev Mat. 6, (2022) 064404). The electronic properties of such materials can be properly tuned with external stimuli such as temperature, pressure, and magnetic field, or by changing the chemistry of the crystal’s constituents. In this presentation, we will discuss both the effects of chemical and physical pressure and magnetic field effects on the magnetism and phase transition properties of the RMn6Sn6 phases, particularly focusing on both ternary and pseudo-ternary (RR’)Mn6Sn6. |
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