S. Wakimoto

Neutron-scattering study of spin-density wave order in the superconducting state of excess-oxygen-doped La{sub 2}CuO{sub 4+y}

We report neutron-scattering measurements of spin-density wave order within the superconducting state of a single crystal of predominately stage-4 La{sub 2}CuO{sub 4+y} with a T{sub c} (onset) of 42 K. The low-temperature elastic magnetic scattering is incommensurate with the lattice and is characterized by long-range order in the copper-oxide plane with the spin direction identical to that in the insulator. Between neighboring planes, the spins exhibit short-range correlations with a stacking arrangement reminiscent of that in the undoped antiferromagnetic insulator. The elastic magnetic peak intensity appears at the same temperature within the errors as the superconductivity, suggesting that the two phenomena are strongly correlated. These observations directly reveal the persistent influence of the antiferromagnetic order as the doping level increases from the insulator to the superconductor. In addition, our results confirm that spin-density wave order for incommensurabilities near 1/8 is a robust feature of the La{sub 2}CuO{sub 4}-based superconductors. {copyright} {ital 1999} {ital The American Physical Society}

Neutron and X-ray Scattering Studies of Relaxors

The extensive and wide-ranging neutron and x-ray scattering studies of relaxors carried out by Gen Shirane and his collaborators are reviewed. Among the many results they have reported in some 50 scientific papers published since 1999, there are three especially notable accomplishments; namely, the discovery of a monoclinic phase near the morphotropic phase boundary, the clarification of the existence and roles of transverse optic soft-mode phonons, and detailed studies of polar nanoregions particularly by diffuse scattering techniques. We will focus mostly on the above topics, and discuss the impact of these on the research and understanding of relaxors.

AMATERAS: A Cold-Neutron Disk Chopper Spectrometer

AMATERAS is a new disk-chopper-type spectrometer installed at Materials and Life Science Experimental Facility (MLF) of J-PARC. AMATERAS is equipped with an extra chopper for pulse shaping at the upstream position, in addition to a monochromating chopper, which conventional chopper spectrometers at pulsed source have. Owing to the use of these choppers and the high peak intensity from a coupled moderator source at MLF, the AMATERAS design realizes high-intensity and high-energy-resolution measurements in quasielastic and inelastic neutron scattering experiments. The spectrometer had the first neutron beam in May 2009. During the course of commissioning, the performance of the spectrometer was confirmed by conducting test experiments. AMATERAS is now open to users and is producing scientific outputs.

Versatile helimagnetic phases under magnetic fields in cubic perovskite SrFeO 3

A helical spin texture is of great current interest for a host of novel spin-dependent transport phenomena. We report a rich variety of nontrivial helimagnetic phases in the simple cubic perovskite

Disappearance of antiferromagnetic spin excitations in overdoped La2-xSrxCuO4.

{\mathrm{SrFeO}}_{3}

Distinct doping dependences of the pseudogap and superconducting gap of La 2 − x Sr x Cu O 4 cuprate superconductors

under magnetic fields up to 42 T. Magnetic and resistivity measurements revealed that the proper-screw spin phase proposed for

Magnetic dispersion of the diagonal incommensurate phase in lightly doped La2-xSrxCuO4.

{\mathrm{SrFeO}}_{3}

Systematic study of short-range antiferromagnetic order and the spin-glass state in lightly dopedLa2−xSrxCuO4

can be subdivided into at least five kinds of ordered phases. Near the multicritical point, an unconventional anomalous Hall effect was found to show up and was interpreted as due to a possible long-period noncoplanar spin texture with scalar spin chirality.

Inelastic neutron scattering study on the resonance mode in an optimally doped superconductor LaFeAsO0.92F0.08

Magnetic excitations for energies up to approximately 100 meV are studied for overdoped La(2-x)Sr(x)CuO(4) with x=0.25 and 0.30, using time-of-flight neutron spectroscopy. Comparison of spectra integrated over the width of an antiferromagnetic Brillouin zone demonstrates that the magnetic scattering at intermediate energies, 20 <or= omega <or= 100 meV, progressively decreases with overdoping. This strongly suggests that the magnetism is not related to Fermi surface nesting, but rather is associated with a decreasing volume fraction of (probably fluctuating) antiferromagnetic bubbles.

Spiral spin structures and origin of the magnetoelectric coupling in YMn2O5

We have performed a temperature-dependent angle-integrated photoemission study of lightly-doped to heavily-overdoped La