Origin of the quantum-critical transition in the bilayer Heisenberg model

Wetensch. publicatieFaculteit der Wiskunde en Natuurwetenschappe

Charge-versus spin driven stripe order: the role of transversal spin fluctuations

Theoretical Physic

Charge- versus spin-driven stripe order: Role of transversal spin fluctuations

Wetensch. publicatieFaculteit der Wiskunde en Natuurwetenschappe

Quantum magnetism in the stripe phase: Bond versus site order

Wetensch. publicatieFaculteit der Wiskunde en Natuurwetenschappe

Glassy nature of stripe ordering in La(1.6-x)Nd(0.4)Sr(x)CuO(4)

We present the results of neutron-scattering studies on various aspects of crystalline and magnetic structure in single crystals of La(1.6-x)Nd(0.4)Sr(x)CuO(4) with x=0.12 and 0.15. In particular, we have reexamined the degree of stripe order in an x=0.12 sample. Measurements of the width for an elastic magnetic peak show that it saturates at a finite value below 30 K, corresponding to a spin-spin correlation length of 200 A. A model calculation indicates that the differing widths of magnetic and (previously reported) charge-order peaks, together with the lack of commensurability, can be consistently explained by disorder in the stripe spacing. Above 30 K, the width of the nominally elastic signal begins to increase. Interpreting the signal as critical scattering from slowly fluctuating spins, the temperature dependence of the width is consistent with renormalized classical behavior of a 2-dimensional anisotropic Heisenberg antiferromagnet. Inelastic scattering measurements show that incommensurate spin excitations survive at and above 50 K, where the elastic signal is neglible. We also report several results related to the LTO-to-LTT transition.Comment: 13 pp, 2-col. REVTeX, 11 figures embedded with psfig; expanded discussion of T-dep. of magnetic peak width; version to appear in Phys. Rev. B (01Jun99

Origin of the quantum-critical transition in the bilayer Heisenberg model

Wetensch. publicatieFaculteit der Wiskunde en Natuurwetenschappe