New spin model for the biased self-avoiding walk (original) (raw)
Related papers
Relaxor ferroelectric behavior in Ca-dopedTbMnO3
Physical Review B, 2008
Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.
First-principles study of magnetic interactions in cupric oxide
Physical Review B, 2012
Cupric oxide (CuO) has been described as belonging to the quasi-one-dimensional antiferromagnetic compounds. It has also been suggested that cupric oxide possesses strong magnetic anisotropy, which is possibly related to the observed ferroelectricity in this material. In this paper, the magnetic interactions of CuO are investigated using the embedded cluster approach. Accurate wave-function-based methods have been employed to describe the interactions along all copper-oxygen chain directions. Both two-center and three-center clusters are considered in our calculations. The antisymmetric anisotropic interaction parameters are also calculated for the two-center clusters by applying an effective Hamiltonian theory. Our results show that the magnetic interactions are dominated by the antiferromagnetic coupling between copper ions along the chain of largest Cu-O-Cu angles in agreement with experiment. The results for the interplane magnetic interactions reveal competition between nearest-neighbor ferromagnetic coupling and second-nearest-neighbor antiferromagnetic interaction along the direction where two copper ions are connected via doubly bridged oxygen ligands. We also find nonnegligible Dzyaloshinskii-Moriya interactions with magnitude comparable to the weak isotropic interchain interactions.
Förster transfer and the local optical density of states in erbium-doped silica
Physical Review B, 2005
Optically excited erbium ions incorporated near the surface of a silica glass decay by spontaneous emission and-at high Er concentration-via Förster energy transfer to quenching sites. By externally modifying the photonic microstructure we vary the local optical density of states ͑LDOS͒ in samples with different degrees of Förster transfer. Changes in spontaneous emission rate are consistent with calculated variations in LDOS at 1.5 m, while Förster energy transfer is not affected by the LDOS. The latter is attributed to the fact that Förster transfer involves virtual photons with a broad energy spectrum, excluding a special role for the LDOS at the atom's transition frequency.
Symmetry disquisition on theTiOXphase diagram(X=Br,Cl)
Physical Review B, 2007
The sequence of phase transitions and the symmetry of, in particular, the low temperature incommensurate and spin-Peierls phases of the quasi-one-dimensional inorganic spin-Peierls system TiOX ͑X = Br and Cl͒ have been studied using inelastic light scattering experiments. The anomalous first-order character of the transition to the spin-Peierls phase is found to be a consequence of the different symmetries of the incommensurate and spin-Peierls ͑P2 1 / m͒ phases. The pressure dependence of the lowest transition temperature strongly suggests that magnetic interchain interactions play an important role in the formation of the spin-Peierls and the incommensurate phases. Finally, a comparison of Raman data on VOCl to the TiOX spectra shows that the high energy scattering previously observed has a phononic origin.
Magnetodielectric coupling of a polar organic-inorganic hybrid Cr(II) phosphonate
Physical Review B, 2008
Cr͓͑H 3 N-͑CH 2 ͒ 2-PO 3 ͒͑Cl͒͑H 2 O͔͒ represents a rare example of a polar organic-inorganic hybrid material that exhibits a canted antiferromagnetic order below T N = 5.5 K. The unusual coexistence of a polar crystal structure and magnetic order triggered our investigation of the magnetodielectric coupling. The coupling is evidenced by an anomaly in the temperature dependence of the dielectric constant below the Néel temperature. The magnetocapacitance is enhanced by one order of magnitude below T N. The main characteristics of the magnetodielectic response are interpreted by Landau theoretical coupling terms.
Physical Review B, 1996
In the present work the reversal of magnetization and the coherence of tunneling when an external magnetic field is rotated instantaneously are studied in systems of a few spin-1/2 particles described by an anisotropic Heisenberg Hamiltonian at Tϭ0. Our calculations demonstrate that this model for small magnetic particles exhibits collective tunneling of the magnetization only for some specific resonant values of the applied magnetic field. These resonant effects occur at fields much lower than the values corresponding to the vanishing of the barrier in the Stoner-Wohlfarth model. The former model is at variance with the exact calculations presented in this paper.
Equilibrium current vortices in simple metals doped with rare earths
Physical Review B
Dilute alloys of rare earths have played a vital role in understanding magnetic phenomena. Here, we model the ground state of dilute 4 f rare-earth impurities in light metals. When the 4 f subshells are open (but not half-filled), the spin-orbit coupling imprints a rotational charge current of conduction electrons around rare-earth atoms. The sign and amplitude of the current oscillate similar to the Ruderman-Kittel-Kasuya-Yosida (RKKY) spin polarization. We compute the observable effect, namely, the Ørsted field generated by the current vortices and the Knight shift.
X-ray spectroscopy at the Mn K edge in LaMnO 3 : An ab initio study
2001
We present ab initio quantum chemical embedded cluster calculations of Mn core-valence and d-d transitions in LaMnO 3. The results are also important for the analysis of recent x-ray absorption and x-ray scattering experiments at the Mn K edge in LaMnO 3. We find that the first two peaks of the pre-edge region correspond to majority-spin and minority-spin e g (3d) states on adjacent Mn ions. For on-site 1s to 4p transitions we find that the ordering of the p components is due to the Jahn-Teller distortion. We also show that the 1s→4p transitions are split due to 3d-4p exchange interactions.