367 research outputs found
Magnon Planar Hall Effect and Anisotropic Magnetoresistance in a Magnetic Insulator
Electrical resistivities can be different for charge currents travelling
parallel or perpendicular to the magnetization in magnetically ordered
conductors or semiconductors, resulting in the well-known planar Hall effect
and anisotropic magnetoresistance. Here, we study the analogous anisotropic
magnetotransport behavior for magnons in a magnetic insulator
YFeO. Electrical and thermal magnon injection, and
electrical detection methods are used at room temperature with transverse and
longitudinal geometries to measure the magnon planar Hall effect and
anisotropic magnetoresistance, respectively. We observe that the relative
difference between magnon current conductivities parallel and perpendicular to
the magnetization, with respect to the average magnon conductivity, i.e.
, is approximately 5% with the majority of the measured devices showing
.Comment: 18 pages, 16 figure
Detection of DC currents and resistance measurements in longitudinal spin Seebeck effect experiments on Pt/YIG and Pt/NFO
In this work we investigated thin films of the ferrimagnetic insulators YIG
and NFO capped with thin Pt layers in terms of the longitudinal spin Seebeck
effect (LSSE). The electric response detected in the Pt layer under an
out-of-plane temperature gradient can be interpreted as a pure spin current
converted into a charge current via the inverse spin Hall effect. Typically,
the transverse voltage is the quantity investigated in LSSE measurements (in
the range of \mu V). Here, we present the directly detected DC current (in the
range of nA) as an alternative quantity. Furthermore, we investigate the
resistance of the Pt layer in the LSSE configuration. We found an influence of
the test current on the resistance. The typical shape of the LSSE curve varies
for increasing test currents.Comment: 4 pages, 2 figure
Nonlocal magnon-polaron transport in yttrium iron garnet
The spin Seebeck effect (SSE) is observed in magnetic insulator|heavy metal
bilayers as an inverse spin Hall effect voltage under a temperature gradient.
The SSE can be detected nonlocally as well, viz. in terms of the voltage in a
second metallic contact (detector) on the magnetic film, spatially separated
from the first contact that is used to apply the temperature bias (injector).
Magnon-polarons are hybridized lattice and spin waves in magnetic materials,
generated by the magnetoelastic interaction. Kikkawa et al. [Phys. Rev. Lett.
\textbf{117}, 207203 (2016)] interpreted a resonant enhancement of the local
SSE in yttrium iron garnet (YIG) as a function of the magnetic field in terms
of magnon-polaron formation. Here we report the observation of magnon-polarons
in \emph{nonlocal} magnon spin injection/detection devices for various
injector-detector spacings and sample temperatures. Unexpectedly, we find that
the magnon-polaron resonances can suppress rather than enhance the nonlocal
SSE. Using finite element modelling we explain our observations as a
competition between the SSE and spin diffusion in YIG. These results give
unprecedented insights into the magnon-phonon interaction in a key magnetic
material.Comment: 5 pages, 6 figure
Argon metastable dynamics in a filamentary jet micro-discharge at atmospheric pressure
Space and time resolved concentrations of Ar () metastable atoms at
the exit of an atmospheric pressure radio-frequency micro-plasma jet were
measured using tunable diode laser absorption spectroscopy. The discharge
features a coaxial geometry with a hollow capillary as an inner electrode and a
ceramic tube with metal ring as outer electrode. Absorption profiles of
metastable atoms as well as optical emission measurements reveal the dynamics
and the filamentary structure of the discharge. The average spatial
distribution of Ar metastables is characterized with and without a target in
front of the jet, showing that the target potential and therewith the electric
field distribution substantially changes the filaments' expansion. Together
with the detailed analysis of the ignition phase and the discharge's behavior
under pulsed operation, the results give an insight into the excitation and
de-excitation mechanisms
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