3,365 research outputs found
Temperature-dependent properties of the magnetic order in single-crystal BiFeO3
We report neutron diffraction and magnetization studies of the magnetic order
in multiferroic BiFeO3. In ferroelectric monodomain single crystals, there are
three magnetic cycloidal domains with propagation vectors equivalent by
crystallographic symmetry. The cycloid period slowly grows with increasing
temperature. The magnetic domain populations do not change with temperature
except in the close vicinity of the N{\P}eel temperature, at which, in
addition, a small jump in magneti- zation is observed. No evidence for the
spin-reorientation transitions proposed in previous Raman and dielectric
studies is found. The magnetic cycloid is slightly anharmonic for T=5 K. The
an- harmonicity is much smaller than previously reported in NMR studies. At
room temperature, a circular cycloid is observed, within errors. We argue that
the observed anharmonicity provides important clues for understanding
electromagnons in BiFeO3.Comment: In Press at PR
Tunneling magnetoresistance in (La,Pr,Ca)MnO3 nanobridges
The manganite (La,Pr,Ca)MnO3 is well known for its micrometer scale phase
separation into coexisting ferromagnetic metallic and antiferromagnetic
insulating (AFI) regions. Fabricating bridges with widths smaller than the
phase separation length scale has allowed us to probe the magnetic properties
of individual phase separated regions. We observe tunneling magnetoresistance
across naturally occurring AFI tunnel barriers separating adjacent
ferromagnetic regions spanning the width of the bridges. Further, near the
Curie temperature, a magnetic field induced metal-to-insulator transition among
a discrete number of regions within the narrow bridges gives rise to abrupt and
colossal low-field magnetoresistance steps at well defined switching fields.Comment: 13 pages, 3 figures, submitted to Applied Physics Letter
Cross-Kerr-based information transfer processes
The realization of nonclassical states is an important task for many
applications of quantum information processing. Usually, properly tailored
interactions, different from goal to goal, are considered in order to
accomplish specific tasks within the general framework of quantum state
engineering. In this paper we remark on the flexibility of a cross-Kerr
nonlinear coupling in hybrid systems as an important ingredient in the
engineering of nonclassical states. The general scenario we consider is the
implementation of high cross-Kerr nonlinearity in cavity-quantum
electrodynamics. In this context, we discuss the possibility of performing
entanglement transfer and swapping between a qubit and a continuous-variable
state. The recently introduced concept of entanglement reciprocation is also
considered and shown to be possible with our scheme. We reinterpret some of our
results in terms of applications of a generalized Ising interaction to systems
of different nature.Comment: 8 pages, 4 figures, RevTeX
Spin-lattice order in frustrated ZnCr2O4
Using synchrotron X-rays and neutron diffraction we disentangle spin-lattice
order in highly frustrated ZnCrO where magnetic chromium ions occupy
the vertices of regular tetrahedra. Upon cooling below 12.5 K the quandary of
anti-aligning spins surrounding the triangular faces of tetrahedra is resolved
by establishing weak interactions on each triangle through an intricate lattice
distortion. The resulting spin order is however, not simply a N\'{e}el state on
strong bonds. A complex co-planar spin structure indicates that antisymmetric
and/or further neighbor exchange interactions also play a role as ZnCrO
resolves conflicting magnetic interactions
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