title: Square vortex lattice at anomalously low magnetic fields in electron-doped Nd1.85Ce0.15CuO4.
abstract: We report here on the first direct observations of the vortex lattice in the bulk of electron-doped Nd1.85Ce0.15CuO4 single crystals. Using small-angle neutron scattering, we have observed a square vortex lattice with the nearest neighbors oriented at 45 degrees from the Cu-O bond direction, which is consistent with theories based on the d-wave superconducting gap. However, the square symmetry persists down to unusually low magnetic fields. Moreover, the diffracted intensity from the vortex lattice is found to decrease rapidly with increasing magnetic field.
authors.affiliation: Laboratory for Neutron Scattering, ETH Zurich and PSI Villigen, CH-5232 Villigen PSI, Switzerland.
authors.forename: R
authors.initials: R
authors.lastname: Gilardi
authors.forename: J
authors.initials: J
authors.lastname: Mesot
authors.forename: S P
authors.initials: SP
authors.lastname: Brown
authors.forename: E M
authors.initials: EM
authors.lastname: Forgan
authors.forename: A
authors.initials: A
authors.lastname: Drew
authors.forename: S L
authors.initials: SL
authors.lastname: Lee
authors.forename: R
authors.initials: R
authors.lastname: Cubitt
authors.forename: C D
authors.initials: CD
authors.lastname: Dewhurst
authors.forename: T
authors.initials: T
authors.lastname: Uefuji
authors.forename: K
authors.initials: K
authors.lastname: Yamada