320 research outputs found
Quantitative analysis of ferroelectric domain imaging with piezoresponse force microscopy
The contrast mechanism for ferroelectric domain imaging via piezoresponse
force microscopy (PFM) is investigated. A novel analysis of PFM measurements is
presented which takes into account the background caused by the experimental
setup. This allows, for the first time, a quantitative, frequency independent
analysis of the domain contrast which is in good agreement with the expected
values for the piezoelectric deformation of the sample and satisfies the
generally required features of PFM imaging
Spin-1/2 Triangular Lattice with Orbital Degeneracy in a Metallic Oxide Ag2NiO2
A novel metallic and magnetic transition metal oxide Ag2NiO2 is studied by
means of resistivity, magnetic susceptibility, specific heat and X-ray
diffraction. The crystal structure is characterized by alternating stacking of
a Ni3+O2 layer and a (Ag2)+ layer, the former realizing a spin-1/2 triangular
lattice with eg orbital degeneracy and the latter providing itinerant
electrons. It is found that the NiO2 layer exhibits orbital ordering at Ts =
260 K and antiferromagnetic spin ordering at TN = 56 K. Moreover, a moderately
large mass enhancement is found for the itinerant electrons, suggesting a
significant contribution from the nearly localized Ni 3d state to the Ag 5s
state that forms a broad band.Comment: 9 pages, 5 figures, to be published in Rapid Communications, Phys.
Rev.
Crosstalk Correction in Atomic Force Microscopy
Commercial atomic force microscopes usually use a four-segmented photodiode
to detect the motion of the cantilever via laser beam deflection. This read-out
technique enables to measure bending and torsion of the cantilever separately.
A slight angle between the orientation of the photodiode and the plane of the
readout beam, however, causes false signals in both readout channels, so-called
crosstalk, that may lead to misinterpretation of the acquired data. We
demonstrate this fault with images recorded in contact mode on ferroelectric
crystals and present an electronic circuit to compensate for it, thereby
enabling crosstalk-free imaging
Impact of Electrostatic Forces in Contact Mode Scanning Force Microscopy
In this contribution we address the question to what extent surface
charges affect contact-mode scanning force microscopy measurements. % We
therefore designed samples where we could generate localized electric field
distributions near the surface as and when required. % We performed a series of
experiments where we varied the load of the tip, the stiffness of the
cantilever and the hardness of the sample surface. % It turned out that only
for soft cantilevers could an electrostatic interaction between tip and surface
charges be detected, irrespective of the surface properties, i.\,e. basically
regardless its hardness. % We explain these results through a model based on
the alteration of the tip-sample potential by the additional electric field
between charged tip and surface charges
Sol-Gel Derived Ferroelectric Nanoparticles Investigated by Piezoresponse Force Microscopy
Piezoresponse force microscopy (PFM) was used to investigate the
ferroelectric properties of sol-gel derived LiNbO nanoparticles. To
determine the degree of ferroelectricity we took large-area images and
performed statistical image-analysis. The ferroelectric behavior of single
nanoparticles was verified by poling experiments using the PFM tip. Finally we
carried out simultaneous measurements of the in-plane and the out-of-plane
piezoresponse of the nanoparticles, followed by measurements of the same area
after rotation of the sample by 90 and 180. Such
measurements basically allow to determine the direction of polarization of
every single particle
Precision nanoscale domain engineering of lithium niobate via UV laser induced inhibition of poling
Continuous wave ultraviolet (UV) laser irradiation at lambda=244 nm on the +z face of undoped and MgO doped congruent lithium niobate single crystals has been observed to inhibit ferroelectric domain inversion. The inhibition occurs directly beneath the illuminated regions, in a depth greater than 100 nm during subsequent electric field poling of the crystal. Domain inhibition was confirmed by both differential domain etching and piezoresponse force microscopy. This effect allows the formation of arbitrarily shaped domains in lithium niobate and forms the basis of a high spatial resolution micro-structuring approach when followed by chemical etching
Anomalous temperature evolution of the internal magnetic field distribution in the charge-ordered triangular antiferromagnet AgNiO2
Zero-field muon-spin relaxation measurements of the frustrated triangular
quantum magnet AgNiO2 are consistent with a model of charge disproportionation
that has been advanced to explain the structural and magnetic properties of
this compound. Below an ordering temperature of T_N=19.9(2) K we observe six
distinct muon precession frequencies, due to the magnetic order, which can be
accounted for with a model describing the probable muon sites. The precession
frequencies show an unusual temperature evolution which is suggestive of the
separate evolution of two opposing magnetic sublattices.Comment: 4 pages, 3 figure
Contrast Mechanisms for the Detection of Ferroelectric Domains with Scanning Force Microscopy
We present a full analysis of the contrast mechanisms for the detection of
ferroelectric domains on all faces of bulk single crystals using scanning force
microscopy exemplified on hexagonally poled lithium niobate. The domain
contrast can be attributed to three different mechanisms: i) the thickness
change of the sample due to an out-of-plane piezoelectric response (standard
piezoresponse force microscopy), ii) the lateral displacement of the sample
surface due to an in-plane piezoresponse, and iii) the electrostatic tip-sample
interaction at the domain boundaries caused by surface charges on the
crystallographic y- and z-faces. A careful analysis of the movement of the
cantilever with respect to its orientation relative to the crystallographic
axes of the sample allows a clear attribution of the observed domain contrast
to the driving forces respectively.Comment: 8 pages, 8 figure
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