2,548 research outputs found
Current-induced persistent magnetization in a relaxorlike manganite
A single crystal of 7% Fe-doped
(LaPr)CaMnO shows up as a typical relaxor
ferromagnet, where ferromagnetic metallic and charge-orbital-ordered insulating
clusters coexist with controllable volume fraction by external stimuli. There,
the persistent ferromagnetic metallic state can be produced by an
electric-current excitation as the filamentary region, the magnetization in
which is increased by ~0.4 per Mn. A clear distinction from the
current heating effect in a magnetic field, which conversely leads to a
decrease in ferromagnetic fraction, enables us to bi-directionally switch both
the magnetization and resistance by applying the voltages with different
magnitudes.Comment: 4 pages, 3 figure
Influence of length and measurement geometry on magnetoimpedance in La0.7Sr0.3MnO3
We show that ac magnetoresistance at room temperature in La0.7Sr0.3MnO3 is
extremely high (= 47% in H = 100 mT, f = 3-5 MHz), and magnetic field
dependence of reactance exhibits a double peak behavior. However, magnitudes of
the ac magnetoresistance and magnetoreactance for a fixed length of the sample
(li) decrease with decreasing separation (lv) between voltage probes unlike the
dc magnetoresistance. On the contrary, change in li has a negligible influence
on magnetoimpedance when lv is fixed. Our results indicate that high frequency
electrical transport is sensitive to local variations in the magnetic
permeability.Comment: 12 pages, 3 figure
Dephasing in a quantum dot coupled to a quantum point contact
We investigate a dephasing mechanism in a quantum dot capacitively coupled to
a quantum point contact. We use a model which was proposed to explain the 0.7
structure in point contacts, based on the presence of a quasi-bound state in a
point contact. The dephasing rate is examined in terms of charge fluctuations
of electrons in the bound state. We address a recent experiment by
Avinun-Kalish {\it et al.} [Phys. Rev. Lett. {\bf 92}, 156801 (2004)], where a
double peak structure appears in the suppressed conductance through the quantum
dot. We show that the two conducting channels induced by the bound state are
responsible for the peak structure.Comment: 4 pages, 2 figure
Electronic band structure and Fermi surface of AgPbO
We present electronic band structure of AgPbO with layered
hexagonal structure containing one-dimensional chains and two-dimensional
Kagom\'{e} layers of silver. A half-filled conduction band shows extremely
simple, single nearly-free-electron-like Fermi surface. The conduction band is
composed of an antibonding state of Pb- and O- mixing with Ag-4d and
. Mass enhancement in the state density at the Fermi energy is expected to
be negligibly small by comparing with the specific-heat data. Calculated Fermi
velocity is consistent with small anisotropy observed in transport properties.
Doping effects on the electronic structure are also discussed.Comment: 6 pages, 9 figures; fig7 replaced, reference 6 adde
Magnetic digital flop of ferroelectric domain with fixed spin chirality in a triangular lattice helimagnet
Ferroelectric properties in magnetic fields of varying magnitude and
direction have been investigated for a triangular-lattice helimagnet
CuFe1-xGaxO2 (x=0.035). The magnetoelectric phase diagrams were deduced for
magnetic fields along [001], [110], and [1-10] direction, and the in-plane
magnetic field was found to induce the rearrangement of six possible
multiferroic domains. Upon every 60-degree rotation of in-plane magnetic field
around the c-axis, unique 120-degree flop of electric polarization occurs as a
result of the switch of helical magnetic q-vector. The chirality of spin helix
is always conserved upon the q-flop. The possible origin is discussed in the
light of the stable structure of multiferroic domain wall.Comment: 5 pages, 4 figures. Accepted in Phys. Rev. Let
Temperature and Field Dependence of Magnetic Domains in LaSrMnO
Colossal magnetoresistance and field-induced ferromagnetism are well
documented in manganite compounds. Since domain wall resistance contributes to
magnetoresistance, data on the temperature and magnetic field dependence of the
ferromagnetic domain structure are required for a full understanding of the
magnetoresistive effect. Here we show, using cryogenic Magnetic Force
Microscopy, domain structures for the layered manganite
LaSrMnO as a function of temperature and magnetic
field. Domain walls are suppressed close to the Curie temperature T, and
appear either via the application of a c-axis magnetic field, or by decreasing
the temperature further. At temperatures well below T, new domain walls,
stable at zero field, can be formed by the application of a c-axis field.
Magnetic structures are seen also at temperatures above T: these features
are attributed to inclusions of additional Ruddleston-Popper manganite phases.
Low-temperature domain walls are nucleated by these ferromagnetic inclusions.Comment: 6 figure
Specific heat study of spin-structural change in pyrochlore NdMoO
By measurements of specific heat, we have investigated the magnetic field
() induced spin-structural change in NdMoO that shows
spin-chirality-related magneto-transport phenomena. A broad peak around 2 K
caused by the ordering of 2-in 2-out structure of the Nd moments at zero
shifts to the lower temperature () up to around 3 T and then to the higher
above around 3 T with increasing for all the direction of . This is
due to the crossover from antiferromagnetic to ferromagnetic arrangement
between the Nd and Mo moments. While the peak increases monotonically above
3 T for //[100], another peak emerges around 0.9 K at 12 T for //[111],
which is ascribed to the ordering of 3-in 1-out structure. For //[110], a
spike like peak is observed at around 3 T, which is caused perhaps by some spin
flip transition.Comment: 5 pages, 4 figure
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