923 research outputs found
Perovskite Manganites Hosting Versatile Multiferroic Phases with Symmetric and Antisymmetric Exchange Strictions
Complete magnetoelectric (ME) phase diagrams of orthorhombic MnO
with and without magnetic moments on the ions have been established. Three
kinds of multiferroic ground states, the -cycloidal, the -cycloidal,
and the collinear -type phases, have been identified by the distinct ME
responses. The electric polarization of the -type phase dominated by the
symmetric spin exchange () is more than 10 times as
large as that of the -cycloidal phase dominated by the antisymmetric one
(), and the ME response is enhanced near the
bicritical phase boundary between these multiferroic phases of different
origins. These findings will provide an important clue for the development of
the magnetically induced multiferroics.Comment: 5 pages, 3 figure
Magnetic-field induced competition of two multiferroic orders in a triangular-lattice helimagnet MnI2
Magnetic and dielectric properties with varying magnitude and direction of
magnetic field H have been investigated for a triangular lattice helimagnet
MnI2. The in-plane electric polarization P emerges in the proper screw magnetic
ground state below 3.5 K, showing the rearrangement of six possible
multiferroic domains as controlled by the in-plane H. With every 60-degree
rotation of H around the [001]-axis, discontinuous 120-degree flop of P-vector
is observed as a result of the flop of magnetic modulation vector q. With
increasing the in-plane H above 3 T, however, the stable q-direction changes
from q|| to q||, leading to a change of P-flop patterns under
rotating H. At the critical field region (~3 T), due to the phase competition
and resultant enhanced q-flexibility, P-vector smoothly rotates clockwise twice
while H-vector rotates counter-clockwise once.Comment: 4 pages, 3 figures. Accepted in Physical Review Letter
Electromagnons in the multiferroic state of perovskite manganites with symmetric-exchange striction
We have investigated electrically-active magnetic excitations
(electromagnons) in perovskite manganites with the -type (up-up-down-down)
spin structure by terahertz spectroscopy. EuYMnO (0.11) and YLuMnO (01) without magnetic -moments,
which host collinear sinusoidal, -type, cycloidal, and -type spin orders,
are used to examine the systematics of possible electromagnons. Three-peak
structures (23, 35, 45 cm) of magnetic origin show up in the -type
phase with little composition () dependence of frequencies, making a
contrast with the electromagnons observed in the cycloidal-spin ()
phases. One of these electromagnon is ascribed to the zone-edge magnon mode
based on the calculated magnon dispersions.Comment: 5 pages, 4 figure
Electromagnons in the multiferroic state of perovskite manganites with symmetric-exchange striction
We have investigated electrically-active magnetic excitations
(electromagnons) in perovskite manganites with the -type (up-up-down-down)
spin structure by terahertz spectroscopy. EuYMnO (0.11) and YLuMnO (01) without magnetic -moments,
which host collinear sinusoidal, -type, cycloidal, and -type spin orders,
are used to examine the systematics of possible electromagnons. Three-peak
structures (23, 35, 45 cm) of magnetic origin show up in the -type
phase with little composition () dependence of frequencies, making a
contrast with the electromagnons observed in the cycloidal-spin ()
phases. One of these electromagnon is ascribed to the zone-edge magnon mode
based on the calculated magnon dispersions.Comment: 5 pages, 4 figure
Electrons doped in cubic perovskite SrMnO3: isotropic metal versus chainlike ordering of Jahn-Teller polarons
Single crystals of electron-doped SrMnO3 with a cubic perovskite structure
have been systematically investigated as the most canonical
(orbital-degenerate) double-exchange system, whose ground states have been
still theoretically controversial. With only 1-2% electron doping by Ce
substitution for Sr, a G-type antiferromagnetic metal with a tiny spin canting
in a cubic lattice shows up as the ground state, where the Jahn-Teller polarons
with heavy mass are likely to form. Further electron doping above 4%, however,
replaces this isotropic metal with an insulator with tetragonal lattice
distortion, accompanied by a quasi-one-dimensional 3z^2-r^2 orbital ordering
with the C-type antiferromagnetism. The self-organization of such dilute
polarons may reflect the critical role of the cooperative Jahn-Teller effect
that is most effective in the originally cubic system.Comment: 5 pages, 4 figure
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