483 research outputs found
Versatile helimagnetic phases under magnetic fields in cubic perovskite SrFeO3
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 SrFeO3 under magnetic fields
up to 42 T. Magnetic and resistivity measurements revealed that the
proper-screw spin phase proposed for SrFeO3 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.Comment: 5 pages, 5 figures, Physical Review B in pres
Systematic Study of Short Range Antiferromagnetic Order and The Spin-Glass State in Lightly Doped La2-xSrxCuO4
Systematic measurements of the magnetic susceptibility were performed on
single crystals of lightly doped La2-xSrxCuO4 (x=0.03, 0.04 and 0.05). For all
samples the temperature dependence of the in-plane magnetic susceptibility
shows typical spin-glass features with spin-glass transition temperatures Tg of
6.3K, 5.5K and 5.0K for x=0.03, 0.04 and 0.05, respectively. The canonical
spin-glass order parameter extracted from the in-plane susceptibility of all
the samples follows a universal scaling curve. On the other hand, the
out-of-plane magnetic susceptibility deviates from Curie law below a
temperature Tdv, higher than Tg. Comparing with previous neutron scattering
results with an instrumental energy resolution of 0.25 meV from Wakimoto et
al., the x-dependence of Tdv is qualitatively the same as that of Tel, the
temperature below which the elastic magnetic scattering develops around (pi,
pi). Thus, a revised magnetic phase diagram in the lightly doped region of
La2-xSrxCuO4 is proposed. The Curie constants calculated from the in-plane
susceptibility are independent of the Sr concentration. On the basis of the
cluster spin-glass model, this fact might reflect an inhomogeneous distribution
of doped holes in the CuO2 plane, such as in a stripe structure.Comment: 7 pages, 6 figure
Field-induced transition between magnetically disordered and ordered phases in underdoped La(2-x)SrxCuO4
We report the observation of a magnetic-field-induced transition between
magnetically disordered and ordered phases in slightly under-doped
La(2-x)SrxCuO4 with x=0.144. Static incommensurate spin-density-wave order is
induced above a critical field of about 3 T, as measured by elastic neutron
scattering. Our results allow us to constrain the location of a quantum
critical point on the phase diagram.Comment: 10 pages, 2 figures; discussion on the location of a quantum critical
point is revise
Charge excitations associated with charge stripe order in the 214-type nickelate and superconducting cuprate
Charge excitations were studied for stipe-ordered 214 compounds,
LaSrNiO and 1/8-doped La(Ba, Sr)CuO
using resonant inelastic x-ray scattering in hard x-ray regime. We have
observed charge excitations at the energy transfer of 1 eV with the momentum
transfer corresponding to the charge stripe spatial period both for the
diagonal (nikelate) and parallel (cuprates) stripes. These new excitations can
be interpreted as a collective stripe excitation or charge excitonic mode to a
stripe-related in-gap state.Comment: 5 pages, 4 figure
Field-induced quantum critical route to a Fermi liquid in high-temperature superconductors
In high transition temperature (T_c) superconductivity, charge doping is a
natural tuning parameter that takes copper oxides from the antiferromagnet to
the superconducting region. In the metallic state above T_c the standard
Landau's Fermi-liquid theory of metals as typified by the temperature squared
(T^2) dependence of resistivity appears to break down. Whether the origin of
the non-Fermi-liquid behavior is related to physics specific to the cuprates is
a fundamental question still under debate. We uncover a new transformation from
the non-Fermi- to a standard Fermi-liquid state driven not by doping but by
magnetic field in the overdoped high-T_c superconductor Tl_2Ba_2CuO_{6+x}. From
the c-axis resistivity measured up to 45 T, we show that the Fermi-liquid
features appear above a sufficiently high field which decreases linearly with
temperature and lands at a quantum critical point near the superconductivity's
upper critical field -- with the Fermi-liquid coefficient of the T^2 dependence
showing a power-law diverging behavior on the approach to the critical point.
This field-induced quantum criticality bears a striking resemblance to that in
quasi-two dimensional heavy-Fermion superconductors, suggesting a common
underlying spin-related physics in these superconductors with strong electron
correlations.Comment: 6 pages, 4 figure
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