1,812 research outputs found
Comparative study of ordered and disordered Y1-xSrxCoO3-d
We have succeeded in preparing A-site ordered- and disordered-Y1/4Sr3/4CoO3-d
with various oxygen deficiencies delta, and have made comparative study of
their structural and physical properties. In the A-site ordered structure,
oxygen vacancies order, and d = 0.34 sample shows a weak ferromagnetic
transition beyond 300 K. On the other hand, in the A-site disordered structure,
no oxygen vacancy ordering is observed, and d = 0.16 sample shows a
ferromagnetic metallic transition around 150 K. A-site disordering destroys the
orderings of oxygen-vacancies and orbitals, leading to the strong modification
of the electronic phases.Comment: 3 pages, 3 figures, proceeding of 52nd Mangetism and Magnetic
Materials Conference (MMM 2007), published in Journal of Applied Physic
Reduction of critical field for magnetic and orbital-ordering phase transition in impurity-substituted NdSrMnO crystal
We have investigated the Mn-site substitution effect in
NdSrMnO single crystal, which has an -type layered
antiferromagnetic (-AFM) phase with the 3-type orbital-order.
Substitution of Fe or Ga for Mn-site suppresses both the -AFM order and
competing ferromagnetic (FM) correlation whereas Cr substitution suppresses
only the -AFM order but reactivates the underlying FM correlation via
double-exchange mechanism along the AFM coupled -direction. In
NdSrMnCrO, the -AFM state with the
orbital-order is changed into the orbital-disordered three-dimensional FM
metallic state by applying magnetic field of T, which is much
smaller than that of the parent compound NdSrMnO.Comment: 5 pages, 4 figures, to appear in APL Material
Cr-doping effect on the orbital fluctuation of heavily doped Nd1-xSrxMnO3 (x ~ 0.625)
We have investigated the Cr-doping effect of Nd0.375Sr0.625MnO3 near the
phase boundary between the x2-y2 and 3z2-r2 orbital ordered states, where a
ferromagnetic correlation and concomitant large magnetoresistance are observed
owing to orbital fluctuation. Cr-doping steeply suppresses the ferromagnetic
correlation and magnetoresistance in Nd0.375Sr0.625Mn1-yCryO3 with 0 < y <
0.05, while they reappear in 0.05 < y < 0.10. Such a reentrant behavior implies
that a phase boundary is located at y = 0.05, or a phase crossover occurs
across y = 0.05.Comment: 3 pages, 3 figures, to be published in Journal of Applied Physic
Refinement Type Inference via Horn Constraint Optimization
We propose a novel method for inferring refinement types of higher-order
functional programs. The main advantage of the proposed method is that it can
infer maximally preferred (i.e., Pareto optimal) refinement types with respect
to a user-specified preference order. The flexible optimization of refinement
types enabled by the proposed method paves the way for interesting
applications, such as inferring most-general characterization of inputs for
which a given program satisfies (or violates) a given safety (or termination)
property. Our method reduces such a type optimization problem to a Horn
constraint optimization problem by using a new refinement type system that can
flexibly reason about non-determinism in programs. Our method then solves the
constraint optimization problem by repeatedly improving a current solution
until convergence via template-based invariant generation. We have implemented
a prototype inference system based on our method, and obtained promising
results in preliminary experiments.Comment: 19 page
Magnetoelectric Properties of (CaSr)CoSiO Crystals
We have investigated the magnetoelectric properties of
(CaSr)CoSiO () crystals with a
quasi-two-dimensional structure. In CaCoSiO (), a canted
antiferromagnetic transition occurs at 5.6 K. The transition temperature
is increasing with increasing Sr concentration, and the rises of
the magnetization and dielectric constant become larger. Since the dielectric
constant shows large change at and the magnetocapacitance effect is
observed below , a coupling between the magnetism and dielectricity
is strong in (CaSr)CoSiO. The positive
magnetocapacitance is reduced by Sr substitution, and is not observed in . Namely, the compound of does not show the
magnetic-field-induced electric polarization. On the other hand, the negative
magnetocapacitance is enhanced by Sr substitution.Comment: 4 pages, 2figures, proceeding of International Conference on
Magnetism 200
Magnetic-field-induced switching between ferroelectric phases in orthorhombic-distortion-controlled MnO
We have investigated the dielectric and magnetic properties of
EuYMnO the presence of the 4 magnetic
moments of the rare earth ions, and have found two ferroelectric phases with
polarization along the and axes in a zero magnetic field. A magnetic
field induced switching from one to the other ferroelectric phase took plase in
which the direction of ferroelectric polarization changed from the a axis to
the c axis by the application of magnetic fields parallel to the a axis. In
contrast to the case of TbMnO, in which the 4 moments of Tb
ions play an important role in such a ferroelectric phase switching, the
magnetic-field-induced switching between ferroelectric phases in
EuYMnO does not originate from the magnetic
transition of the rare-earth 4 moments, but from that of the Mn 3 spins.Comment: 8 pages, 3 figures, RevTeX4, Proceedings of MMM 2005, to appear in J.
Appl. Phy
Enhancement of the anomalous Hall effect and spin glass behavior in the bilayered manganite La(2-2x)Sr(1+2x)Mn2O7
The Hall resistivity and magnetization have been investigated in the
ferromagnetic state of the bilayered manganite La(2-2x)Sr(1+2x)Mn2O7 (x=0.36).
The Hall resistivity shows an increase in both the ordinary and anomalous Hall
coefficients at low temperatures below 50K, a region in which experimental
evidence for the spin glass state has been found in a low magnetic field of
1mT. The origin of the anomalous behavior of the Hall resistivity relevant to
magnetic states may lie in the intrinsic microscopic inhomogeneity in a
quasi-two-dimensional electron system.Comment: 7 pages, 4 figures, Solid State Communications (in press
Internal magnetic field effect on magnetoelectricity in orthorhombic crystals
We have investigated the role of the 4 moment on the magnetoelectric (ME)
effect of orthorhombic MnO (=rare earth ions). In order to clarify
the role of the 4 moment, we prepared three samples: (Eu,Y)MnO without
the 4 moment, TbMnO with the anisotropic 4 moment, and
(Gd,Y)MnO with the isotropic 4 moment. The ferroelectric behaviors of
these samples are different from each other in a zero magnetic field.
(Eu,Y)MnO and (Gd,Y)MnO show the ferroelectric polarization along
the a axis in the ground state, while TbMnO shows it along the c axis.
Such difference may arise from the influence of the anisotropic Tb 4
moment. The direction of the ferroelectric polarization of MnO is
determined by the internal magnetic field arising from the 4 moment.Comment: 2 pages, 1 figure, the proceeding of International Conference of
Magnetism, to be published in the Journal of Magnetism and Magnetic Material
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