Dzialoshinski-Moriya Interaction Research Articles

Critical behavior of the in-plane weak ferromagnet Sr2IrO4

Critical behavior of the single-layered Sr2IrO4, which exhibits weak ferromagnetism in the ab plane, is investigated by the bulk magnetization study. Critical exponents β=0.284±0.008 and γ=1.726±0.004 with the critical temperature TC=230.8±0.9 are obtained by the Kouvel–Fisher method, and δ=4.443±0.008 is generated by the critical isotherm analysis at TC=231K. The obtained critical exponents of Sr2IrO4 are close to prediction of the theoretical model with {d:n}={2:1} (where d is the partial dimensionality and n is the spin dimensionality), which indicates one-dimensional ferromagnetic interaction in the two-dimensional layered material. On the other hand, the critical exponents lie between the prediction of long-range and short-range models, indicating that the short-range Heisenberg interaction alone cannot totally describe the critical behavior. It is suggested that the Dzialoshinsky–Moriya interaction caused by rotation of the octahedra and the symmetric anisotropy result into a lower spatial short-range interaction, which competes with the long-range interaction caused by expansion of 5d orbits.

Tripartite entanglement of a spin star model with Dzialoshinski–Moriya interaction

The effect of Dzialoshinski---Moriya (DM) interaction on the tripartite thermal entanglement of a spin-star model with four spins has been analyzed by an entanglement measure of the tripartite negativity. Our results imply that the tripartite thermal entanglement can be established among the three surrounding parties which do not interact with each other but interact with the central party independently. From the results, we find that the strong DM interaction can enhance the tripartite thermal entanglement while the high temperature can shrink it. The effect of the inhomogeneous coupling on the tripartite thermal entanglement is also discussed.

Effect of Dzialoshinski–Moriya interaction on the quantum discord of a spin-star model

The effect of Dzialoshinski–Moriya (DM) interaction on the quantum discord and the thermal entanglement of the density matrix of a spin star model is investigated. Our results imply that the quantum correlation measured by quantum discord and thermal entanglement can be established between two surrounding parties both of which have no interaction with each other but interact with the central party independently. From the analysis, we find that the strong DM interaction can enhance the quantum discord and thermal entanglement while the external magnetic field with a large value and the high temperature can shrink them. Specially, the quantum discord is more robust than the thermal entanglement in the sense that the range of parameters in which the quantum discord takes a zero value is much smaller than that of the thermal entanglement.

QUANTUM INFORMATION TRANSFER IN A TWO-PARALLEL SPIN-CHAIN CHANNEL WITH INTERNAL AND EXTERNAL EFFECTS

With the effects of Dzialoshinski–Moriya interaction and external magnetic field, the entanglement transfer has been investigated in a parallel spin-chain system. Our results imply that the perfect transfer can be realized at some special times, and the transfer time can be greatly condensed with the rising of the spin-orbit coupling strength. The entanglement sudden death phenomenon is sensitive to the initial condition. In addition, due to the application of magnetic field on the channel spins, the reliability and efficiency of the transmission are greatly challenged.

Thermal Entanglement of a Two-Qubit XXZ Heisenberg Chain with Dzialoshinski–Moriya Interaction

The effect of Dzialoshinski–Moriya (DM) interaction on thermal entanglement of a two-qubit XXZ spin chain in a homogenous magnetic field is investigated. It is found that the DM interaction can enhance thermal entanglement. When D is large enough, the entanglement can exist for larger temperatures and strong magnetic field.

Thermal Entanglement of an XY Two-Qutrit Spin Chain with Dzialoshinski–Moriya Interaction

The effect of Dzialoshinski–Moriya (DM) interaction on thermal entanglement of an XY two-qutrit spin chain is investigated. We find that DM interaction and the anisotropy parameter can enhance quantum thermal entanglement to a maximal value individually. However, when both of them take large values, the entanglement is not enhanced, but is destroyed. Our analysis will shed some light on the understanding of the effect of the DM interaction on thermal entanglement of an XY two-qutrit spin chain.

Inelastic Neutron Scattering, EPR and Spin Chirality in Spin-Frustrated V3 and Cu3 Nanomagnets with Dzialoshinsky-Moriya Exchange

The inelastic neutron scattering (INS) and EPR transitions are considered for the spin-frustrated V3 and Cu3 nanomagnets. It is shown that the DM exchange and distortions determine the Q-dependence and redistribution of the intensities of the intra- and inter-doublet INS transitions in the 2(S=1/2) states as well as the intensities of the EPR transitions. The peculiarities of the INS and EPR spectra of the V3 ring of V15 quantum molecular magnet and EPR spectra of the V3 and Cu3 nanomagnets are described by the isosceles Heisenberg model with the DM exchange. Spin chirality and spin structure of the Cu3 and V3 nanomagnets with the Dzialoshinsky-Moriya (DM) exchange interaction are analysed in the vector and scalar spin chirality models. The vector chirality model describes the field, orientation and deformation dependence of the spin chirality κn. The spin chirality is formed by the DM interaction and depends on the sign of the DM parameter Gz. The DM exchange and distortions determine the degree of chirality κn<1 in the isosceles clusters.

Spin-frustrated V3 and Cu3 nanomagnets with Dzialoshinsky–Moriya exchange. 2. Spin structure, spin chirality and tunneling gaps

The spin chirality and spin structure of the Cu3 and V3 nanomagnets with the Dzialoshinsky–Moriya (DM) exchange interaction are analyzed. The correlations between the vector κ and the scalar χ chirality are obtained. The DM interaction forms the spin chirality which is equal to zero in the Heisenberg clusters. The dependences of the spin chirality on magnetic field and deformations are calculated. The cluster distortions reduce the spin chirality. The vector chirality is reduced partially and the scalar chirality vanishes in the transverse magnetic field. In the isosceles clusters, the DM exchange and distortions determine the sign and degree of the spin chirality κ. The correlations between the chirality parameters κn and the intensities of the EPR and INS transitions are obtained. The vector chirality κn describes the spin chirality of the Cu3 and V3 nanomagnets, the scalar chirality describes the pseudoorbital moment of the DM cluster. It is shown that in the consideration of the DM exchange, the spin states DM mixing and tunneling gaps at level crossing fields depend on the coordinate system of the DM model. The calculations in the DM exchange models in the right-handed and left-handed frame show opposite magnetic behavior at the level crossing field and allow to explain the opposite schemes of the tunneling gaps and levels crossing, which have been obtained in different treatments. The results of the DM model in the right-handed frame are consistent with the results of the group-theoretical analysis, whereas the results in the left-handed frame are inconsistent with that. The correlations between the spin chirality of the ground state and tunneling gaps at the level crossing field are obtained for the equilateral and isosceles nanoclusters.

Effect of Dzialoshinski-Moriya interaction on thermal entanglement of a mixed-spin chain

The effect of Dzialoshinski-Moriya (DM) interaction on thermal entanglement of a mixed-spin chain in an external magnetic field is investigated. It is found that DM interaction may enhance quantum thermal entanglement to a maximal value even though the magnetic field plays a positive role in shrinking thermal entanglement in the mixed-spin chain. Furthermore, the effect of inhomogeneity of the magnetic field on quantum entanglement is analyzed. Our analysis will shed some light on the understanding of the effect of the DM interaction on thermal entanglement of a mixed-spin chain.

Thermal entanglement of a two-qutrit Ising system with Dzialoshinski–Moriya interaction

Thermal entanglement of a two-qutrit Ising system in the presence of an external homogeneous magnetic field and Dzialoshinski–Moriya (DM) interaction is investigated. Influences of magnetic field, temperature, and DM interaction on the entanglement have been characterized in terms of negativity for a wide range of parameters. The cases of parallel, antiparallel and transverse magnetic fields are considered. Results of detailed numerical calculations are explained using the analytically determined ground and excited states of the system. It is shown that at a given temperature, control of entanglement can be optimized by utilizing competing effects of the magnetic field and the DM interaction.

Spin-Frustrated Trinuclear Cu(II) Clusters with Mixing of 2(S = 1/2) and S = 3/2 States by Antisymmetric Exchange. 1. Dzialoshinsky−Moriya Exchange Contribution to Zero-Field Splitting of the S = 3/2 State

The mixing of the spin-frustrated 2(S = 1/2) and S = 3/2 states by the Dzialoshinsky-Moriya (DM) exchange is considered for the Cu 3(II) clusters with strong DM exchange coupling. In the antiferromagnetic Cu 3 clusters with strong DM interaction, the 2(S = 1/2)-S = 3/2 mixing by the in-plane DM exchange ( G x ) results in the large positive contribution 2 D DM > 0 to the axial zero-field splitting (ZFS) 2 D of the S = 3/2 state. The correlations between the ZFS 2 D DM of the excited S = 3/2 state, sign of G z and chirality of the ground-state were obtained. In the isosceles Cu 3 clusters, the in-plane DM exchange mixing results in the rhombic magnetic anisotropy of the S = 3/2 state. Large distortions result in an inequality of the pair DM parameters, that leads to an additional magnetic anisotropy of the S = 3/2 state. In the {Cu 3} nanomagnet, the in-plane DM exchange (Gx, Gy) mixing results in the 58% contribution 2 D DM to the observed ZFS 2 D of the S = 3/2 state. The DM exchange and distortions explain the experimental observation that the intensities of the electron paramagnetic resonance (EPR) transitions arising from the 2(S = 1/2) group of levels of the {Cu 3} nanomagnet are comparable to each other and are 1 order of magnitude weaker than that of the S = 3/2 state. In the ferromagnetic Cu 3 clusters, the in-plane DM exchange mixing of the excited 2(S = 1/2) and the ground S = 3/2 states results in the large negative DM exchange contribution 2 D DM' < 0 to the axial ZFS 2 D of the ground S = 3/2 state.

Thermal entanglement of a two-qutrit XX spin chain with Dzialoshinski–Moriya interaction

The effect of Dzialoshinski–Moriya (DM) interaction on thermal entanglement of a two-qutrit XX spin chain in a homogenous magnetic field is investigated. Our results imply that DM interaction and the magnetic field play competing roles in enhancing thermal entanglement.

Interpretation of the experimental magnetic properties of spin [formula omitted] square lattice (K 2V 2O 5) by means of small square lattice spin theory

Experimental results of magnetization and magnetic susceptibility of the square spin lattice can be interpreted by using a Heisenberg Hamiltonian for a small 4×4 square lattice. We find that the agreement between theory and experiments is remarkable, as in the case with the one-dimensional ring. We also treat the symmetry breaking Dzialoshinski–Moriya interaction, which is present in the 2D square lattice antiferromagnet K 2V 2O 5, using mean field theory. Surprisingly we find good agreement between theory and experiment. By combining experimental and theoretical results one can determine the coupling constants of the Hamiltonian.

Collinear to Spiral Spin Transformation without Changing the Modulation Wavelength upon Ferroelectric Transition inTb1−xDyxMnO3

Lattice modulation and magnetic structures in magnetoelectric compounds Tb1-xDyxMnO3 have been studied around the ferroelectric (FE) Curie temperature TC by x-ray and neutron diffraction. Temperature-independent modulation vectors through TC are observed for the compounds with 0.50 <or=x<or=0.68. This indicates that ferroelectricity with a polarization (P) along the c axis in the RMnO3 series cannot be ascribed to such an incommensurate-commensurate transition of an antiferromagnetic order as was previously anticipated. A neutron diffraction study with x=0.59 shows that the FE transition is accompanied by the transformation of the Mn-spin alignment from sinusoidal (collinear) antiferromagnetism into a transverse-spiral structure. The observed spiral structure below TC is expected to produce P along the c axis with the "inverse" Dzialoshinski-Moriya interaction, which is consistent with observation.

Ferroelectric Phase Transition and New Intermediate Phase in Bi-Layered Perovskite SrBi 2 Ta 2 O 9

Thermal and structural studies showed that SrBi 2 Ta 2 O 9 undergoes ferroelectric-intermediate and intermediate-paraelectric phase transitions at 608 K ( T c ) and 850 K ( T *), respectively, while Bi-rich Sr 0.85 Bi 2.1 Ta 2 O 9 at 510 K ( T o ) and 670 K ( T c ). On heating, SrBi 2 Ta 2 O 9 still remains to be orthorhombic above T c, and then changes to tetragonal above T *. The TaO 6 is a distorted octaheron along the c -axis even in the paraelectric phase, and locates in antiparallel manner above T *. Below T c, this crystal favors canted arrangements of TaO 6, resulting in the net polarization along the a -axis. It was clarified that SrBi 2 Ta 2 O 9 shows a canted weak ferroelectricity, analogous to weak ferromagnetism with Dzialoshinski-Moriya interaction.

Weak ferromagnetism in poly(3-methylthiophene)(PMTh)

Ferromagnetic behaviour at 300 K has been observed from SQUID experiments in ClO 4 - doped PMTh. The samples were prepared electrochemically at 25 °C in acetonitrile with 0.1M LiClO 4 and then partially reduced. Atomic absorption analysis discards magnetic particles contamination. Hysteresis curves were observed for pressed pellets in all range of temperatures (300K-2K). The remanence at 300 K and pressed at 250 bar was around 8.06x10 -4 emu/g with coercitivity of 130 Oe. The influence of water content in the solvent during the sample synthesis and the pressure is shown. We discuss a model that explains our data in terms of the anisotropic superexchange Dzialoshinski-Moriya interaction giving rise to weak ferromagnetism.,.

Single Crystal Magnetic Susceptibility of 1-D [PM·Cu(NO3)2·(H2O)2

Single crystal studies of the magnetic susceptibility of the chain compound [PM·Cu(NO3)2·(H2O)2]n (PM = pyrimidine) show that it is a good example of a uniform S=1/2 antiferromagnetic Heisenberg chain, characterised by a single exchange parameter |2J|/kB= 36 K. The Cu g-tensor principal values are g= 2.34(2) and g| =2.05(2). In the low-T region a divergent contribution to the susceptibility (Curie tail) is observed that exhibits a pronounced anisotropy. This Curie tail cannot be reconciled assuming chain defects or impurities as its origin. It rather appears intrinsic to the chains and associated with the relative canting of the local g-tensors of neighbouring Cu ions and the Dzialoshinski-Moriya interaction. Our study constitutes evidence for a staggered contribution to the susceptibility which has been predicted theoretically recently.

Normal-state anomalies in the transport and magnetic properties in the(La1−xPrx)1.85Sr0.15CuO4system and their correlation withTcsuppression: A signature of the effects of orthorhombic distortions

The correlation between the normal-state anomalies observed in the magnetic and transport properties of the $({\mathrm{La}}_{1\ensuremath{-}x}{\mathrm{Pr}}_{x}{)}_{1.85}{\mathrm{Sr}}_{0.15}{\mathrm{CuO}}_{4}$ system with $0l~xl~0.5$ was studied. The x-ray-diffraction patterns revealed a linear increase of the $(a\ensuremath{-}b)$ orthorhombic parameter with the Pr content. The resistivity curves showed an increasing deviation from linearity below \ensuremath{\sim}100 K. This anomaly was properly accounted by a logarithmic term, whose coefficient C linearly increases with x. Superconducting quantum interference device measurements of the normal-state magnetic susceptibility evidenced a deviation from the ${\mathrm{Pr}}^{3+}$ Curie-Weiss behavior in the same temperature range for which the resistivity anomaly occurs. This behavior is explained in terms of an induced magnetic moment at the ${\mathrm{CuO}}_{2}$ layers under strain. A Dzialoshinsky-Moriya interaction, associated to the orthorhombic distortions, is proposed to be the source of a weak canted ferromagnetic component, which develops in conjunction with an enhancement of the antiferromagnetic correlations. A comprehensive picture of the conduction mechanism for the whole system is presented in terms of a Kondo-like scattering of the mobile holes by the spin fluctuations at the conduction planes. ${T}_{c}$ suppression was found to correlate with C, suggesting that the excitation which interacts with the carriers in the normal state is relevant for superconductivity.

Soliton in an inhomogeneous weak ferromagnet with the Dzialoshinski-Moriya interaction.

We have identified an integrable model of the inhomogeneous radially symmetric weak Heisenberg ferromagnet in arbitrary $n$ dimensions with Dzialoshinski-Moriya antisymmetric spin coupling. The elementary spin excitations of the magnet are found to be governed by soliton modes under small-angle oscillation of the antisymmetric spin coupling.

Reaction-diffusion processes described by three-state quantum chains and integrability

The master equation of one-dimensional three-species reaction-diffusion processes is mapped onto an imaginary-time Schr\"odinger equation. In many cases the Hamiltonian obtained is that of an integrable quantum chain. Within this approach we search for all $3$-state integrable quantum chains whose spectra are known and which are related to diffusive-reactive systems.Two integrable models are found to appear naturally in this context: the $U_{q}\widehat{SU(2)}$-invariant model with external fields and the $3$-state $U_q Su(P/M)$-invariant Perk-Schultz models with external fields. A nonlocal similarity transformation which brings the Hamiltonian governing the chemical processes to the known standard forms is described, leading in the case of periodic boundary conditions to a generalization of the Dzialoshinsky-Moriya interaction.