scholarly journals Elementary excitations and thermodynamics of zig-zag spin ladders with alternating nearest-neighbor exchange interactions

2009 ◽  
Vol 35 (6) ◽  
pp. 455-467 ◽  
Author(s):  
A. A. Zvyagin ◽  
V. O. Cheranovskii
Keyword(s):  
Nearest Neighbor ◽  
Exchange Interactions ◽  
Elementary Excitations

Asymmetrical Elementary Excitations Responsible for the Ferrimagnetism in an Antiferromagnetic Spin-1/2 Zigzag Ladder

2013 ◽  
Vol 380-384 ◽  
pp. 4262-4267
Author(s):  
Zhong Long Wang ◽  
Qiao Wu ◽  
Lin Jie Ding
Keyword(s):  
Random Phase Approximation ◽  
Nearest Neighbor ◽  
Random Phase ◽  
Exchange Interactions ◽  
Many Body ◽  
Elementary Excitations ◽  
Greens Function ◽  
The Many ◽  
Antiferromagnetic Spin ◽  
Ferrimagnetic Ordering

The finite-temperature magnetic properties of an antiferromagnetic (AF) bond alternating S=1/2 zigzag spin chain with asymmetrical AF next-nearest-neighbor (NNN) exchange interactions in an external magnetic field are investigated by means of the many-body Greens function theory within random phase approximation. The results show that when the NNN exchange interactions are asymmetrical, the spin system exhibit a clear ferrimagnetic ordering at finite temperatures. It is shown that the ferrimagnetic behavior is attributed to asymmetrical elementary excitations, resulting from the competition between the spin frustrations and magnetic excitations reduced by the asymmetrical NNN interactions. The mechanism of this ferrimagnetism is much different from a common one which originates from mixed spins with different spin values through antiparallel spin alignments.

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.

scholarly journals Frustrations and phase transitions in magnets of various dimensionality

2018 ◽  
Vol 185 ◽  
pp. 11002
Author(s):  
Felix Kassan-Ogly ◽  
Alexey Proshkin
Keyword(s):  
Magnetic Field ◽  
Phase Transitions ◽  
External Magnetic Field ◽  
Specific Heat ◽  
Nearest Neighbor ◽  
Linear Chain ◽  
Exchange Interactions ◽  
Specific Model ◽  
Main Challenge ◽  
Transition Points

We studied magnetic orderings, phase transitions, and frustrations in the Ising, 3-state Potts and standard 4-state Potts models on 1D, 2D, and 3D lattices: linear chain, square, triangular, kagome, honeycomb, and body-centered cubic. The main challenge was to find out the causes of frustrations phenomena and those features that distinguish frustrated system from not frustrated ones. The spins may interrelate with one another via the nearest-neighbor, the next-nearest-neighbor or higher-neighbor exchange interactions and via an external magnetic field that may be either competing or not. For problem solving we mainly calculated the entropy and specific heat using the rigorous analytical solutions for Kramers-Wannier transfer-matrix and exploiting computer simulation, par excellence, by Wang-Landau algorithm. Whether a system is ordered or frustrated is depend on the signs and values of exchange interactions. An external magnetic field may both favor the ordering of a system and create frustrations. With the help of calculations of the entropy, the specific heat and magnetic parameters, we obtained the points and ranges of frustrations, the frustration fields and the phase transition points. The results obtained also show that the same exchange interactions my either be competing or noncompeting which depends on the specific model and the lattice topology.

scholarly journals Magnet with Ferromagnetic Nearest-Neighbor and Antiferromagnetic Next-Nearest-Neighbor Exchange Interactions

2009 ◽  
Vol 115 (5) ◽  
pp. 925-930 ◽  
Author(s):  
R. Szymczak ◽  
H. Szymczak ◽  
G. Kamieniarz ◽  
G. Szukowski ◽  
K. Jaśniewicz-Pacer ◽  
...  
Keyword(s):  
Nearest Neighbor ◽  
Exchange Interactions

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 Finitely Correlated Generalized Spin Ladders

1998 ◽  
Vol 12 (23) ◽  
pp. 2325-2348 ◽  
Author(s):  
A. K. Kolezhuk ◽  
H.-J. Mikeska
Keyword(s):  
Ground State ◽  
Ground States ◽  
Exchange Interactions ◽  
Second Order ◽  
Order Transition ◽  
Matrix Product ◽  
Elementary Excitations ◽  
Degenerate Ground State ◽  
Second Order Transition ◽  
Isotropic Exchange

We study two-leg S=1/2 ladders with general isotropic exchange interactions between spins on neighboring rungs, whose ground state can be found exactly in a form of finitely correlated (matrix product) wave function. Two families of models admitting an exact solution are found: one yields translationally invariant ground states and the other describes spontaneously dimerized models with twofold degenerate ground state. Several known models with exact ground states (Majumdar–Ghosh and Shastry–Sutherland spin-1/2 chains, Affleck–Kennedy–Lieb–Tasaki spin-1 chain, Δ-chain, Bose–Gayen ladder model) can be obtained as particular cases from the general solution of the first family, which includes also a set of models with only bilinear interactions. Those two families of models have nonzero intersection, which enables us to determine exactly the phase boundary of the second-order transition into the dimerized phase and to study the properties of this transition. The structure of elementary excitations in the dimerized phase is discussed on the basis of a variational ansatz. For a particular class of models, we present exact wave functions of the elementary excitations becoming gapless at second-order transition lines. We also propose a generalization of the Bose–Gayen model which has a rich phase diagram with all phase boundaries being exact.

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