Magnetic Behavior of the 2-Leg and 3-Leg Spin Ladder Cuprates Srn-1Cun+1O2n

Two-leg ladder systems with dipole-dipole Fermion interactions

The ground-state phase diagram of a two-leg fermionic dipolar ladder with inter-site interactions is studied using density matrix renormalization group (DMRG) techniques. We use a state-of-the-art implementation of the DMRG algorithm and finite size scaling to simulate large system sizes with high accuracy. We also consider two different model systems and explore stable phases in half and quarter filling factors. We find that in the half filling, the charge and spin gaps emerge in a finite value of the dipole-dipole and on-site interactions. In the quarter filling case, s-wave superconducting state, charge density wave, homogenous insulating and phase separation phases occur depend on the interaction values. Moreover, in the dipole-dipole interaction, the D-Mott phase emerges when the hopping terms along the chain and rung are the same, whereas, this phase has been only proposed for the anisotropic Hubbard model. In the half filling case, on the other hand, there is either charge-density wave or charged Mott order phase depends on the orientation of the dipole moments of the particles with respect to the ladder geometry.

A magnetically isolated cuprate spin-ladder system: synthesis, structures, and magnetic properties

Two magnetically isolated cuprate spin ladders have been synthesized. Their crystal structures and preliminary investigation into the magnetic properties were reported.

Dynamic properties of a diluted pyrochlore cooperative paramagnet (Tb(p)Y(1-p))2Ti2O7

Investigations of the spin dynamics of the geometrically frustrated pyrochlore (Tb(p)Y(1-p))2Ti2O7, using muon spin relaxation and neutron spin echo, as a function of magnetic coverage p, have been carried out. Our major finding is that paramagnetic fluctuations prevail as T-->0 for all values of p, and that they are sensitive to dilution, indicating a cooperative spin motion. However, the percolation threshold pc is not a critical point for the fluctuations. We also find that the low temperature spectral density has a 1/f behavior, and that dilution slows down the spin fluctuations.

Crossover from dilute to majority spin freezing in two leg ladder system Sr(Cu,Zn)2O3

Muon spin relaxation has been measured in Sr(Cu1-xZnx)2O3. The results for low Zn concentration x</=0.6% are consistent with freezing of dilute moments, with one Cu spin for each Zn, having approximately 0.5&mgr;(B) frozen moment. A sharp increase of the relaxation rate at T-->0 occurred with increasing x around x approximately 0.8%, accompanied by a change of line shape to that expected in a concentrated magnetic environment. Analyses of the results for x>/=0.8% suggest that the majority of Cu moments participate in spin freezing, yet with a significantly reduced and spatially inhomogeneous moment size having a 1D correlation length xi approximately 6 lattice units, or a 2D correlation area involving approximately 19 Cu spins.

63Cu NQR evidence of dimensional crossover to anisotropic 2D regime in S = 1 / 2 three-Leg ladder Sr2Cu3O5

We probed spin-spin correlations up to 725 K with 63Cu nuclear quadrupole resonance in the S = 1 / 2 three-leg ladder Sr2Cu3O5. We present experimental evidence that below 300 K weak interladder coupling causes dimensional crossover of the spin-spin correlation length xi from the quasi-1D (xi approximately 1 / T) to the anisotropic 2D regime ( xi approximately exp2pirho(s) / T, where 2pirho(s) = 290+/-30 K is the effective spin stiffness).