Bulletin of the American Physical Society
Mid-Atlantic Section Fall Meeting 2020
Volume 65, Number 20
Friday–Sunday, December 4–6, 2020; Virtual
Session F04: Quantum Magnetism I |
Hide Abstracts |
Chair: Valery Kiryukhin, Rutgers University |
Saturday, December 5, 2020 2:00PM - 2:36PM |
F04.00001: Trompe L'oeil Ferromagnetism Invited Speaker: Sang-Wook Cheong The characteristics of ferro-(ferri)magnetism with non-zero magnetization include magnetic attraction, magnetic circular dichroism, and magneto-optical Kerr (MOKE), Faraday, and various anomalous Hall-type (Hall, Ettingshausen, Nernst, and thermal Hall) effects. Non-magnetic or antiferromagnetic materials in external electric fields or other environments (called specimen constituents) can share symmetry operational similarity (SOS) with magnetization in relation to broken symmetries. These specimen constituents can be associated with non-zero magnetization and/or show ferromagnetism-like behaviors, so we say that they exhibit Trompe L'oeil Ferromagnetism. Examples include linear magnetoelectric materials such as Cr$_{\mathrm{2}}$O$_{\mathrm{3}}$ under electric fields, Faraday effect in chiral materials such as tellurium with current flow, magnetic field induced by the motion of Neel- or Bloch-type ferroelectric walls, and magneto-optical Kerr (MOKE), Faraday effect, and/or anomalous Hall-type effects in certain antiferromagnets such as Cr$_{\mathrm{2}}$O$_{\mathrm{3}}$, MnPSe$_{\mathrm{3}}$, Mn$_{\mathrm{4}}$(Nb,Ta)$_{\mathrm{2}}$O$_{\mathrm{9}}$, and Mn$_{\mathrm{3}}$(Sn,Ge,Ga). A large number of new specimen constitutes having SOS with Magnetization will be discussed, and require future experimental verification of their ferromagnetism-like behaviors, and also theoretical understanding of possible microscopic mechanisms. [Preview Abstract] |
Saturday, December 5, 2020 2:36PM - 2:48PM |
F04.00002: Multiorbital Flat Band Ferromagnetism with a Percolation Representation Eric Bobrow, Junjia Zhang, Yi Li We consider a two-layer multiorbital system consisting of a $p_xp_y$-orbital honeycomb lattice layer and an $f$-orbital layer centered on the honeycomb plaquettes. With appropriately tuned layer potentials, the system exhibits a flat band with provably ferromagnetic ground states at half filling of the band in the presence of intra-orbital Hubbard interactions and Hund's coupling. Away from half filling, the interacting system admits a percolation representation, where the ground state space is spanned by maximum-spin clusters of localized single-particle states. A paramagnetic-ferromagnetic transition occurs as the band approaches half filling and the space of degenerate ground states becomes dominated by clusters with macroscopic spin. The critical filling of the flat band where this transition occurs can be found through Monte Carlo simulation for spin-weighted percolation. [Preview Abstract] |
Saturday, December 5, 2020 2:48PM - 3:00PM |
F04.00003: Easily Switchable Giant Magnetism Near Room Temperature Mikel Holcomb, Navid Mottaghi, Ghadendra Bhandari, Guerau Cabrera In many areas of materials science and economics, competition is seen as an opportunity to obtain improved performance. Utilizing many techniques (bulk magnetometry, neutron reflectometry and resonant magnetic scattering), we have discovered and explored the existence of competing magnetic phases in many single layer thin films that results in giant negative magnetization. We have focused on the system of complex oxide La$_{\mathrm{0.7}}$Sr$_{\mathrm{0.3}}$MnO$_{\mathrm{3.}}$ While transmission electron microscopy images show pristine epitaxial growth, the data supports that there are regions of different magnetic order. This results in interesting magnetic measurements, that share similarities with ferrimagnets with competing magnetic lattices. This competition results in spontaneous negative magnetization that aligns counter to a small applied magnetic field and inverted hysteresis loops near room temperature. This behavior has much in common with superparamagnetic nanoparticles. In this talk, the time, field and temperature dependence of these samples will be discussed to help understand this phenomenon. The switch from negative to positive magnetization effectively doubles the change in magnetization, important for some types of devices. We acknowledge funding support from NSF (DMR-1608656) and DOE (DE-SC0016176). [Preview Abstract] |
Saturday, December 5, 2020 3:00PM - 3:12PM |
F04.00004: Non-Kramers doublet ground state of the triangular-lattice spin-liquid candidate TbInO3 Mai Ye, Xianghan Xu, Xiangyue Wang, Jaewook Kim, Sang-Wook Cheong, Girsh Blumberg Ferroelectric insulator TbInO$_3$ has been proposed to be a 2D spin-liquid candidate. This material has a Weiss temperature of -17K, but no magnetic ordering occurs down to 0.1K [Nat. Phys. 15, 262 (2019)]. It remains unclear whether the magnetic lattice has honeycomb or triangular symmetry at low temperature. We study the ground state properties of this system by probing its crystal-field (CF) excitations using inelastic light scattering. The experimentally established CF level scheme provides a satisfactory description for the low-temperature specific heat and entropy data. In particular, we demonstrate that the Tb ions have a non-Kramers doublet ground state, and these doublets from a triangular magnetic lattice. [Preview Abstract] |
Saturday, December 5, 2020 3:12PM - 3:24PM |
F04.00005: DMFTwDFT: An open-source code combining Dynamical Mean Field Theory with various Density Functional Theory packages Uthpala Herath, Vijay Singh, Benny Wah, Xingyu Liao, Aldo Romero, Hyowon Park Dynamical Mean Field Theory (DMFT) is a successful method to compute the electronic structure of strongly correlated materials, especially when it is combined with density functional theory (DFT). Here, we present an open-source computational package (and a library) combining DMFT with various DFT codes interfaced through the Wannier90 package. The correlated subspace is expanded as a linear combination of Wannier functions introduced in the DMFT approach as local orbitals. In particular, we provide a library mode for computing the DMFT density matrix. This library can be linked and then internally called from any DFT package, assuming that a set of localized orbitals can be generated in the correlated subspace. The existence of this library allows developers of other DFT codes to interface with our package and achieve the charge-self-consistency within DFT+DMFT loops. To test and check our implementation, we computed the density of states and the band structure of well-known correlated materials, namely LaNiO$_3$, SrVO$_3$, and NiO. The obtained results are compared to those obtained from other DFT+DMFT implementations. [Preview Abstract] |
Saturday, December 5, 2020 3:24PM - 4:00PM |
F04.00006: Chiral Magnetism: A Geometric Perspective Invited Speaker: Oleg Tchernyshyov Chiral ferromagnets have spatially modulated magnetic order exemplified by helices, spirals, and more complex patterns such as skyrmion crystals. The theoretical understanding of these states is based on a competition of a strong Heisenberg exchange interaction favoring uniform magnetization and a weaker Dzyaloshinskii-Moriya interaction promoting twists in magnetization. We offer a geometric approach, in which chiral forces are a manifestation of curvature in spin parallel transport [1]. The resulting theory is a gauged version of the Heisenberg model, with the Dzyaloshinskii-Moriya vectors serving as background SO(3) gauge fields. This geometrization of chiral magnetism is akin to the treatment of gravity in general theory of relativity, where gravitational interactions are reduced to a curvature of spacetime. An immediate benefit of this geometrical perspective is a simple way to define a conserved spin current in the presence of spin-orbit interaction. We show that the ground state of the gauged Heisenberg model in 2 spatial dimensions is a hexagonal skyrmion crystal in a wide range of applied magnetic fields. The simplicity of the model allows for an efficient analytical treatment of this problem using standard field-theoretic methods. Monte Carlo simulations confirm our analytical arguments. [1] D. Hill, V. Slastikov, and O. Tchernyshyov, arXiv:2008.08681. [Preview Abstract] |
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