Interactions In Spin Systems Research Articles

N-Vicinity Method for Ising Model with Long-Range Interaction

The previously developed n-vicinity method [3] allows us to calculate accurately critical values of inverse temperatures for Ising models with short-range interaction. We generalize the method to the case of long-range interactions in spin systems and obtain theoretical formulas for the inverse temperatures in terms of the spin interaction constants. The comparison of our theoretical estimates with computer simulations for the two- and three-dimensional Ising models shows that the larger the dimension of the problem the better their agreement.

Minimal models of α−Li2IrO3 : Range of interactions, ground state properties, and magnetization processes

In recent years, a lot of effort has been devoted to the quest for experimental realizations of Kitaev interactions in spin systems. Recently, many materials have been synthesized which seem to realize extended Kitaev models, where Kitaev interactions are supplemented by Heisenberg and other bond dependent terms. The crystal and electronic structure of these materials renders the determination of a minimal model a non trivial pursuit. In this work, we will concentrate on one of these particular materials, $\alpha$-Li$_2$IrO$_3$, for which various minimal models have been proposed. Employing large scale Monte Carlo simulations we show how the number of prospective models can be reduced. We study in detail six models with different range of the interactions, and show how only two of those reproduce the most recent experimental results for this material. We obtain two possible minimal models, one of them with nearest neighbour interactions, while the other includes interactions up to third neighbours. Furthermore, we show that strong bond anisotropies and further neighbour interactions are crucial to stabilize the tilted counterotating spirals found in $\alpha$-Li$_2$IrO$_3$. We further clarify the picture, and distinguish these two models by studying the magnetization processes. We predict the magnetization behaviour of these models, and propose future experimental directions.

Thermal entanglement properties of small spin clusters

Exchange interactions in spin systems can give rise to quantum entanglement in the ground and thermal states of the systems. In this paper, we consider a spin tetramer, with spins of magnitude 1/2, in which the spins interact via nearest-neighbour, diagonal and four-spin interactions of strength J1, J2 and K respectively. The ground and thermal state entanglement properties of the tetramer are calculated analytically in the various limiting cases. Signatures of quantum phase transition (QPT) in terms of appropriate entanglement measures are obtained. The magnetic properties of a S = 1/2 AFM polyoxovanadate compound, V12, are well explained by spin tetramers with only nearest-neighbour exchange interactions. Treating the magnetic susceptibility chi as an entanglement witness (EW), an estimate of the lower bound of the critical entanglement temperature, T_c, above which the multipartite entanglement disappears in the experimental compound, is determined. A second EW based on energy provides an estimate of the entanglement temperature T_E, below which bipartite entanglement is certainly present in the system, is determined. The cases of the symmetric trimer and the tetrahedron are also considered.

NQR transient nutation and rotary echoes in the effective field of multiple-pulse sequences

We present the results of the experimental investigations of the transient processes preceding the establishment of quasistationary states in multiple-pulse nuclear quadrupole resonance. It is shown that the inversion of the phase of radio frequency pulses in the pulse sequence or an extra pulse produces the echo signal in the effective field of the multiple-pulse sequence (the echo on the envelope of echo signals). The train of the echo signals in the effective field is also obtained. The application of this technique for the investigation of the dipole-dipole interactions in spin systems with large inhomogeneous broadening is discussed.

Magnetic field dependence of internal interactions in nuclear spin systems

AbstractThe internal interactions in spin systems depend on the magnetic field strength, since the latter perturbs the electronic wave functions. The changes in the interaction tensors are approximately proportional to the applied magnetic field. This effect is experimentally most significant for quadrupolar spin systems, since the quadrupolar interaction is usually the strongest. This field dependence of internal interactions, seldom considered before, may lead to an ambiguity in the explanation of nuclear magnetic resonance (NMR) experiments of quadrupolar spin systems.

Cross-fzlaxation in paramagnetic crystals at low temperatures

The well- known phenomena of cross-relaxation between two sin-systems in paramagnetic crystals is theoretically investigated at low temperatures when Zeeman energy of spins exceeds their heat energy, but there is no order due to spin-spin interactions in spin system.

Disorder and competing interactions in spin systems: Finite‐cluster calculations

physica status solidi (b)Volume 119, Issue 2 p. K159-K163 Short Note Disorder and competing interactions in spin systems: Finite-cluster calculations J. Richter, J. Richter Wissenschaftsbereich Physik der Hochschule für Verkehrswesen “Friedrich List”, Dresden Search for more papers by this author J. Richter, J. Richter Wissenschaftsbereich Physik der Hochschule für Verkehrswesen “Friedrich List”, Dresden Search for more papers by this author First published: 1 October 1983 https://doi.org/10.1002/pssb.2221190253 PSF 103, DDR-8072 Dresden, GDR. AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Volume119, Issue21 October 1983Pages K159-K163 RelatedInformation