Coupled S=1/2S=1/2 Heisenberg antiferromagnetic chains in an effective staggered field

We present a systematic study of coupled $S=1/2$ Heisenberg antiferromagnetic chains in an effective staggered field. We investigate several effects of the staggered field in the {\em higher} ({\em two or three}) {\em dimensional} spin system analytically. In particular, in the case where the staggered field and the inter-chain interaction compete with each other, we predict, using mean-field theory, a characteristic phase transition. The spin-wave theory predicts that the behavior of the gaps induced by the staggered field is different between the competitive case and the non-competitive case. When the inter-chain interactions are sufficiently weak, we can improve the mean-field phase diagram by using chain mean-field theory and the analytical results of field theories. The ordered phase region predicted by the chain mean-field theory is substantially smaller than that by the mean-field theory.Comment: 13pages, 12figures, to be published in PR

Magnetic and thermal properties of 4f-3d ladder-type molecular compounds

We report on the low-temperature magnetic susceptibilities and specific heats of the isostructural spin-ladder molecular complexes L$_{2}$[M(opba)]_{3\cdot xDMSO$\cdot y$H$_{2}$O, hereafter abbreviated with L$_{2}$M$_{3}$ (where L = La, Gd, Tb, Dy, Ho and M = Cu, Zn). The results show that the Cu containing complexes (with the exception of La$_{2}$Cu$_{3}$) undergo long range magnetic order at temperatures below 2 K, and that for Gd$_{2}$Cu$_{3}$ this ordering is ferromagnetic, whereas for Tb$_{2}$Cu$_{3}$ and Dy$_{2}$Cu$_{3}$ it is probably antiferromagnetic. The susceptibilities and specific heats of Tb$_{2}$Cu$_{3}$ and Dy$_{2}$Cu$_{3}$ above $T_{C}$ have been explained by means of a model taking into account nearest as well as next-nearest neighbor magnetic interactions. We show that the intraladder L--Cu interaction is the predominant one and that it is ferromagnetic for L = Gd, Tb and Dy. For the cases of Tb, Dy and Ho containing complexes, strong crystal field effects on the magnetic and thermal properties have to be taken into account. The magnetic coupling between the (ferromagnetic) ladders is found to be very weak and is probably of dipolar origin.Comment: 13 pages, 15 figures, submitted to Phys. Rev.

Synthesis, structure, and magnetic properties of bis(3-amino-2-chloropyridinium) tetrahalocuprate(II) [halide = Cl or Br]

The reaction of CuX₂(X=Cl or Br) with 3-amino-2-chloropyridine in aqueous acids (HX; X=Cl or Br) yields bis(3-amino-2-chloropyridinium)tetrachlorocuprate(II) and bis(3-amino-2- chloropyridinium)tetrabromocuprate(II). Both compounds have been characterized by IR, powder X-ray diffraction, single-crystal X-ray diffraction and temperature dependent magnetic susceptibility. The compounds are isomorphous and exhibit weak antiferromagnetic interactions

LOW TEMPERATURE MAGNETIC SUSCEPTIBILITY OF [(CH3)3NH] 3Cu2Cl7 A ONE DIMENSIONAL S = 1/2 FERROMAGNET

On a mesuré la susceptibilité magnétique d'un composé, en poudre de [(CH3)3NH] 3Cu2Cl7de 2 à 300 K. La susceptibilité diverge fortement à basse température et on l'a interprétée comme due à une chaîne ferromagnétique fortement couplée (J/k = 72 K) d'ions de cuivre en coordination octaédrique plus une chaine antiferromagnétique plus faiblement couplée (J/k = - 13 K) d'ions de cuivre en coordination tétraédrique. Les interactions antiferromagnétiques entre chaines se traduisent par un maximum de χT observé à 3,8 K. Un modèle pour expliquer ce maximum indique un échange très faible (J'/k [MATH] - 0,1 K) entre les chaînes.The magnetic susceptibility of a powdered sample of [(CH3)3NH] 3Cu2Cl7 has been measured from 2-300 K. The susceptibility is strongly divergent at low temperatures and has been interpreted as due to a strongly coupled (J/k = 72 K) ferromagnetic chain of octahedrally coordinated copper ions plus a weakly antiferromagnetic (J/k = - 13 K) chain of tetrahedrally coordinated copper ions. Evidence for antiferromagnetic interactions between chains is seen in the maximum of χT observed at 3.8 K. A model to account for this maximum indicates very weak (J'/k [MATH] - 0.1 K.) interchain exchange

Berezinskii—Kosterlitz—Thouless correlations in copper-based quasi-2D spin systems (Review Article)

We present an overview of selected copper-based quasi-2D square-lattice spin-1/2 materials with an easy-plane anisotropy, providing the possibility to study emergent Berezinskii-Kosterlitz-Thouless (BKT) correlations. In particular, in those materials with a comparatively small exchange coupling, the effective XY anisotropy of the low-temperature spin correlations can be controlled by an applied magnetic field, yielding a systematic evolution of the BKT correlations. In cases where the residual interlayer correlations are small enough, dynamical BKT correlations in the critical regime may be observed experimentally, whereas the completion of the genuine BKT transition is preempted by the onset of long-range order. © 2023 Author(s)

Quantum-critical spin dynamics in a Tomonaga-Luttinger liquid studied with muon-spin relaxation

We demonstrate that quantum-critical spin dynamics can be probed in high magnetic fields using muon-spin relaxation (μ+SR). Our model system is the strong-leg spin ladder bis(2,3-dimethylpyridinium) tetrabromocuprate (DIMPY). In the gapless Tomonaga-Luttinger liquid phase we observe finite-temperature scaling of the μ+SR 1/T1 relaxation rate which allows us to determine the Luttinger parameter K. We discuss the benefits and limitations of local probes compared with inelastic neutron scattering