414 research outputs found
Nanoscale switching characteristics of nearly tetragonal BiFeO3 thin films
We have investigated the nanoscale switching properties of strain-engineered
BiFeO3 thin films deposited on LaAlO3 substrates using a combination of
scanning probe techniques. Polarized Raman spectral analysis indicate that the
nearly-tetragonal films have monoclinic (Cc) rather than P4mm tetragonal
symmetry. Through local switching-spectroscopy measurements and piezoresponse
force microscopy we provide clear evidence of ferroelectric switching of the
tetragonal phase but the polarization direction, and therefore its switching,
deviates strongly from the expected (001) tetragonal axis. We also demonstrate
a large and reversible, electrically-driven structural phase transition from
the tetragonal to the rhombohedral polymorph in this material which is
promising for a plethora of applications.Comment: 10 pages, 6 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
Flexible Supercapacitors: A Materials Perspective
Flexible supercapacitors are highly attractive for the large number of emerging portable lightweight consumer devices. The novelty of a flexible supercapacitor is the incorporation of flexible electrode or substrate material to combine structural flexibility with the inherently high power density of supercapacitors. Flexible supercapacitors can use non-Faradaic energy storage process as seen in the electric double layer capacitor type or a Faradaic mechanism as seen in the pseudocapacitors (PCs). In this review, we account the current progress in pseudocapacitive electrode materials, fabrication techniques and new materials for electric double layer capacitor, and different flexible substrates. Future directions in developing new materials toward improved energy density and cost-effectiveness of the flexible supercapacitors and their usage in combination with lithium-ion batteries are highlighted
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