Magnetic ground state and the spin-state transitions in YBaCo2O5.5

AbstractA recent focus of quantum spin liquid (QSL) studies is how disorder/randomness in a QSL candidate affects its true magnetic ground state. The ultimate question is whether the QSL survives disorder or the disorder leads to a “spin-liquid-like” state, such as the proposed random-singlet (RS) state. Since disorder is a standard feature of most QSL candidates, this question represents a major challenge for QSL candidates. YbMgGaO4, a triangular lattice antiferromagnet with effective spin-1/2 Yb3+ions, is an ideal system to address this question, since it shows no long-range magnetic ordering with Mg/Ga site disorder. Despite the intensive study, it remains unresolved as to whether YbMgGaO4 is a QSL or in the RS state. Here, through ultralow-temperature thermal conductivity and magnetic torque measurements, plus specific heat and DC magnetization data, we observed a residual κ0/T term and series of quantum spin state transitions in the zero temperature limit for YbMgGaO4. These observations strongly suggest that a QSL state with itinerant excitations and quantum spin fluctuations survives disorder in YbMgGaO4.

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A PROBABLE MECHANISM OF SPIN-STATE TRANSITION IN LaCoO3

Modern Physics Letters B ◽

10.1142/s0217984910024146 ◽

2010 ◽

Vol 24 (16) ◽

pp. 1785-1790 ◽

Cited By ~ 1

Author(s):

JIAN NI ◽

CHUN-LAN MA

Keyword(s):

Band Gap ◽

Spin State ◽

Ground State ◽

State Transition ◽

Coulomb Repulsion ◽

Probable Mechanism ◽

Generalized Gradient ◽

Magnetic Ground State ◽

Spin State Transition ◽

Ferromagnetic Ground State

Total energies and electronic structures of rhombohedral lanthanum cobaltite ( LaCoO 3) with both non-magnetic and magnetic states are calculated from generalized gradient approximation (GGA) with on-site Coulomb correlation corrections (GGA + U) method. It is found that only the non-magnetic ground state can be obtained for LaCoO 3 at 5 K, consistent with previous studies. When U = 4.0 eV is employed, the band gap is found to be 0.6 eV, in agreement with the result of ultraviolet photoemission spectroscopy (UPS). The ferromagnetic ground state can be obtained for LaCoO 3 at 100 K, but much larger on-site Coulomb interaction between Co 3d is found. Only when U = 7.8 eV is employed for the calculation of LaCoO 3 at 100 K can we find a band gap of 0.26 eV, consistent with the optical conductivity measurements. According to these results, we propose a probable mechanism for spin-state transition in LaCoO 3 at around 100 K. The transition is mainly due to the big change in the on-site Coulomb repulsion between Co 3d electrons.

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Emergence of a noncollinear magnetic state in twisted bilayer CrI3

10.21203/rs.3.rs-533063/v1 ◽

2021 ◽

Author(s):

Yang Xu ◽

Ariana Ray ◽

Yu-Tsun Shao ◽

Shengwei Jiang ◽

Daniel Weber ◽

...

Keyword(s):

Ground State ◽

Domain Walls ◽

Magnetic State ◽

Twist Angle ◽

Ground States ◽

Memory Storage ◽

State Transitions ◽

Magnetic Memory ◽

Magnetic Ground State ◽

Magnetic States

Abstract The emergence of two-dimensional (2D) magnetic crystals and moiré engineering of van der Waals materials has opened the door for devising new magnetic ground states via competing interactions in moiré superlattices. Although a suite of interesting phenomena, including multi-flavor magnetic states, noncollinear magnetic states, moiré magnon bands and magnon networks, has been predicted in twisted bilayer magnetic crystals, nontrivial magnetic ground states have yet to be realized. Here, by utilizing the stacking-dependent interlayer exchange interactions in CrI3, we demonstrate in small-twist-angle CrI3 bilayers a noncollinear magnetic ground state. It consists of antiferromagnetic (AF) and ferromagnetic (FM) domains and is a result of the competing interlayer AF coupling in the monoclinic stacking regions of the moiré superlattice and the energy cost for forming AF-FM domain walls. Above a critical twist angle of ~ 3°, the noncollinear state transitions to a collinear FM ground state. We further show that the noncollinear magnetic state can be controlled by electrical gating through the doping-dependent interlayer AF interaction. Our results demonstrate the possibility of engineering new magnetic ground states in twisted bilayer magnetic crystals, as well as gate-voltage-controllable high-density magnetic memory storage.

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Magnetic ground state and exchange interactions in the Ising chain ferromagnet CoNb2O6

Physical Review B ◽

10.1103/physrevb.103.064415 ◽

2021 ◽

Vol 103 (6) ◽

Author(s):

Subhash Thota ◽

Sayandeep Ghosh ◽

Maruthi R ◽

Deep C. Joshi ◽

Rohit Medwal ◽

...

Keyword(s):

Ground State ◽

Exchange Interactions ◽

Ising Chain ◽

Magnetic Ground State

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S. Vasudevan, H.N. Vasan and C.N.R. Rao, pes study of spin-state transitions in α6 transition metal complexes and oxides

Chemical Physics Letters ◽

10.1016/0009-2614(80)85319-x ◽

1980 ◽

Vol 71 (1) ◽

pp. 186

Keyword(s):

Transition Metal ◽

Metal Complexes ◽

Transition Metal Complexes ◽

Spin State ◽

State Transitions

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Magnetic Ground State and Electronic Structure Calculations of PbMnO3 Using DFT

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.895.420 ◽

2014 ◽

Vol 895 ◽

pp. 420-423 ◽

Cited By ~ 4

Author(s):

Sathya Sheela Subramanian ◽

Baskaran Natesan

Keyword(s):

Electronic Structure ◽

Band Structure ◽

Fermi Level ◽

Ground State ◽

Density Functional ◽

Electronic Structure Calculations ◽

Magnetic Ground State ◽

Electronic Band ◽

Structure Calculations ◽

Centrosymmetric Structure

Structural optimization, magnetic ground state and electronic structure calculations of tetragonal PbMnO3have been carried out using local density approximation (LDA) implementations of density functional theory (DFT). Structural optimizations were done on tetragonal P4mm (non-centrosymmetric) and P4/mmm (centrosymmetric) structures using experimental lattice parameters and our results indicate that P4mm is more stable than P4/mmm. In order to determine the stable magnetic ground state of PbMnO3, total energies for different magnetic configurations such as nonmagnetic (NM), ferromagnetic (FM) and antiferromagnetic (AFM) were computed for both P4mm and P4/mmm structures. The total energy results reveal that the FM non-centrosymmetric structure is found to be the most stable magnetic ground state. The electronic band structure, density of states (DOS) and the electron localization function (ELF) were calculated for the stable FM structure. ELF revealed the distorted non-centrosymmetric structure. The band structure and DOS for the majority spins of FM PbMnO3showed no band gap at the Fermi level. However, a gap opens up at the Fermi level in minority spin channel suggesting that it could be a half-metal and a potential spintronic candidate.

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