2002/03/29 by H. A. Mook, Pengcheng Dai, S. M. Hayden +6 · 4 citations
Physics and Astronomy · #Advanced Condensed Matter Physics #Magnetic properties of thin films #Physics of Superconductivity and Magnetism #cond-mat.str-el #cond-mat.supr-con
paper · pdf · doi:10.1103/physrevb.66.144513
11 pages with 10 figures
arxiv created 2002/03/29 · openalex publication_date 2002/10/30 · arxiv updated 2009/11/30 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
Polarized and unpolarized neutron diffraction has been used to search for magnetic order in YBa2Cu3O6+x superconductors. Most of the measurements were made on a high quality crystal of YBa2Cu3O6.6. It is shown that this crystal has highly ordered ortho-II chain order, and a sharp superconducting transition. Inelastic scattering measurements display a very clean spin-gap and pseudogap with any intensity at 10 meV being 50 times smaller than the resonance intensity. The crystal shows a complicated magnetic order that appears to have three components. A magnetic phase is found at high temperatures that seems to stem from an impurity with a moment that is in the a\ensuremath-b plane, but disordered on the crystal lattice. A second ordering occurs near the pseudogap temperature that has a shorter correlation length than the high temperature phase and a moment direction that is at least partly along the c axis of the crystal. Its moment direction, temperature dependence, and Bragg intensities suggest that it may stem from orbital ordering of the d-density wave type. An additional intensity increase occurs below the superconducting transition. The magnetic intensity in these phases does not change noticeably in a 7 T magnetic field aligned approximately along the c axis. Searches for magnetic order in YBa2Cu3O7 show no signal while a small magnetic intensity is found in YBa2Cu3O6.45 that is consistent with the c axis directed magnetic order. The results are contrasted with other recent neutron measurements.