D. Senff

Magnetic correlations in La2-xSrxCoO4 studied by neutron scattering: possible evidence for stripe phases.

Spin correlations in La2-xSrxCoO4 (0.3 < or = x < or = 0.6) have been studied by neutron scattering. The commensurate antiferromagnetic order of La2CoO4 persists in a very short range up to a Sr content of x = 0.3, whereas small amounts of Sr suppress commensurate antiferromagnetism in cuprates and in nickelates. La2-xSrxCoO4 with x > 0.3 exhibits incommensurate spin ordering with the modulation closely following the amount of doping. These incommensurate phases strongly resemble the stripe phases observed in cuprates and nickelates, but incommensurate magnetic ordering appears only at larger Sr content in the cobaltates due to a reduced charge mobility.

Magnetic excitations in a cycloidal magnet: the magnon spectrum of multiferroic TbMnO3

The magnetic excitations in multiferroic TbMnO3 have been investigated by inelastic scattering of polarized and unpolarized neutrons in the ferroelectric cycloidal and in the paraelectric collinear phase. The polarization analysis of the excitations at the incommensurate magnetic zone center allows one to determine the characters of three distinct modes. In particular we may identify those modes which may directly couple to the ferroelectric polarization. We find a rather complex magnon dispersion with branches split throughout the Brillouin zone, which should be a generic characteristic of elliptical cycloidal order.

Flop of electric polarization driven by the flop of the Mn spin cycloid in multiferroic TbMnO3.

N. Aliouane, 2 K. Schmalzl, D. Senff, A. Maljuk, K. Prokeš, M. Braden, and D. N. Argyriou ∗ Helmholtz-Zentrum Berlin für Materialen und Energy, Glienicker Str. 100, D-14109 Berlin, Germany Institute For Energy, P.O. Box 40, NO-2027 Kjeller, Norway Institut für Festkörperforschung, Forschungszentrum Jülich GmbH, JCNS at ILL, 38042 Grenoble Cedex 9, France II. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, D-50937 Köln, Germany (Dated: February 11, 2009)

Magnetic and structural transitions in La 1 − x A x CoO 3 ( A = Ca , Sr, and Ba)

We report thermal-expansion, lattice-constant, and specific-heat data of the series

Field dependence of magnetic correlations through the polarization flop transition in multiferroic TbMnO 3 : Evidence for a magnetic memory effect

{\text{La}}_{1\ensuremath{-}x}{A}_{x}{\text{CoO}}_{3}

Spin-wave dispersion in orbitally ordered La1/2Sr3/2MnO4.

for

Evidence for charge orbital and spin stripe order in an overdoped manganite.

0\ensuremath{\le}x\ensuremath{\le}0.30

Melting of magnetic correlations in charge-orbital ordered La 1 / 2 Sr 3 / 2 MnO 4 : Competition of ferromagnetic and antiferromagnetic states

with

Mott-Hubbard versus charge-transfer behavior in LaSrMnO4 studied via optical conductivity

A=\text{Ca}

Polarized-neutron-scattering studies on the chiral magnetism in multiferroic MnWO4

, Sr, and Ba. For the undoped compound