scholarly journals Interplay between spatial anisotropy and next-nearest-neighbor exchange interactions in the triangular Heisenberg model

2020 ◽  
Vol 102 (22) ◽  
Author(s):  
M. G. Gonzalez ◽  
E. A. Ghioldi ◽  
C. J. Gazza ◽  
L. O. Manuel ◽  
A. E. Trumper
Keyword(s):  
Heisenberg Model ◽  
Nearest Neighbor ◽  
Exchange Interactions ◽  
Spatial Anisotropy

scholarly journals Isotropic Nature of the Metallic Kagome Ferromagnet Fe3Sn2 at High Temperatures

Crystals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 307
Author(s):  
Rebecca L. Dally ◽  
Daniel Phelan ◽  
Nicholas Bishop ◽  
Nirmal J. Ghimire ◽  
Jeffrey W. Lynn
Keyword(s):  
Elevated Temperatures ◽  
Magnetocrystalline Anisotropy ◽  
Inelastic Neutron Scattering ◽  
Exchange Interactions ◽  
Inelastic Neutron ◽  
Temperature Threshold ◽  
Magnetic Exchange ◽  
Spatial Anisotropy ◽  
Isotropic Exchange ◽  
State Spin

Anisotropy and competing exchange interactions have emerged as two central ingredients needed for centrosymmetric materials to exhibit topological spin textures. Fe3Sn2 is thought to have these ingredients as well, as it has recently been discovered to host room temperature skyrmionic bubbles with an accompanying topological Hall effect. We present small-angle inelastic neutron scattering measurements that unambiguously show that Fe3Sn2 is an isotropic ferromagnet below TC≈660 K to at least 480 K—the lower temperature threshold of our experimental configuration. Fe3Sn2 is known to have competing magnetic exchange interactions, correlated electron behavior, weak magnetocrystalline anisotropy, and lattice (spatial) anisotropy; all of these features are thought to play a role in stabilizing skyrmions in centrosymmetric systems. Our results reveal that at the elevated temperatures measured, there is an absence of significant magnetocrystalline anisotropy and that the system behaves as a nearly ideal isotropic exchange interaction ferromagnet, with a spin stiffness D(T=480 K)=168 meV Å2, which extrapolates to a ground state spin stiffness D(T=0 K)=231 meV Å2.

Loss of classicality in the alternating spin-½/spin-1 chain, in the presence of next-neighbor couplings and Dzyaloshinskii-Moriya interactions

2022 ◽  
Author(s):  
Abhiroop Lahiri ◽  
Swapan K Pati
Keyword(s):  
Ground State ◽  
Nearest Neighbor ◽  
Spiral Structure ◽  
Exchange Interactions ◽  
Quantum Fluctuations ◽  
Wave Theory ◽  
Range Order ◽  
Density Matrix Renormalization Group ◽  
Density Matrix Renormalization ◽  
Spin Spiral

Abstract We have considered and alternating spin-½/spin-1 chain with nearest-neighbor (J1), next-nearest neighbor (J2) antiferromagnetic Heisenberg interactions along with z-component of the Dzyaloshinskii-Moriya(DM) (Dz) interaction. The Hamiltonian has been studied using (a) Linear Spin-Wave Theory(LSWT) and (b) Density Matrix Renormalization Group (DMRG). The system had been reported earlier as a classical ferrimagnet only when nearest neighbor exchange interactions are present. Both the antiferromagnetic next-nearest neighbor interactions and DM interactions introduce strong quantum fluctuations and due to which all the signatures of ferrimagnetism vanishes. We find that the nonzero J2 introduces strong quantum fluctuations in each of the spin sites due to which the z-components of both spin-1 and spin-1/2 sites average out to be zero. The ground state becomes a singlet. The presence of J1 along with Dzintroduces a short range order but develops long range order along the XY plane. J1 along with J2induces competing phases with structure factor showing sharp and wide peaks, at two different angles reflecting the spin spiral structure locally as well as in the underlying lattice. Interestingly, we find that the Dz term removes the local spin spiral structure in z-direction, while developing a spiral order in the XY plane.

Thermodynamic Properties of an In-Phase Flux Antiferromagnetic Spin Coupled Heisenberg Model on a Square Lattice

SPIN ◽  
2018 ◽  
Vol 08 (04) ◽  
pp. 1830001
Author(s):  
E. Mainimo ◽  
N. Ibrahim Famenyi
Keyword(s):  
Energy Spectrum ◽  
Specific Heat ◽  
Thermodynamic Parameters ◽  
Heisenberg Model ◽  
State Energy ◽  
Spontaneous Magnetization ◽  
Exchange Interactions ◽  
Spin Model ◽  
Square Lattice ◽  
Antiferromagnetic Spin

Using the two-dimensional Jordan–Wigner Fermionization procedure, we calculate the energy spectrum of the in-phase flux antiferromagnetically spin-1/2 coupled Heisenberg model in a square lattice, the formalism used introduces the notion of isotropic parameters. The energy spectrum is analyzed for various regimes of the exchange interactions and the isotropic parameters. The thermodynamic parameters of the lattice, notably the ground state energy, the free energy, mean energy, entropy and specific heat are calculated. It is seen that the specific heat undergoes a phase transition at a temperature below the critical temperature due to spontaneous magnetization. Its entropy for homogeneous and completely isotropic regime is compared for two regimes of the exchange interaction and it is observed that the entropy decreases with an increase in the coupling strength. All the thermodynamic parameters calculated for this spin model are seen to be in conformity with the principles and laws of Statistical Thermodynamics.

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