20 research outputs found
Tailoring epitaxial growth and magnetism in La1-xSrxMnO3 / SrTiO3 heterostructures via temperature-driven defect engineering
Among the class of strongly-correlated oxides, La1-xSrxMnO3 a half
metallic ferromagnet with a Curie temperature above room temperature has
sparked a huge interest as a functional building block for memory storage and
spintronic applications. In this respect, defect engineering has been in the
focus of a long-standing quest for fabricating LSMO thin films with highest
quality in terms of both structural and magnetic properties. Here, we discuss
the correlation between structural defects, such as oxygen vacancies and
impurity islands, and magnetism in La0.74Sr0.26MnO3/SrTiO3 (LSMO/STO) epitaxial
heterostructures by systematic control of the growth temperature and
post-deposition annealing conditions. Upon increasing the growth temperature
within the 500 700 C range, the epitaxial LSMO films experience a
progressive improvement in oxygen stoichiometry, leading to enhanced magnetic
characteristics. Concurrently, however, the use of a high growth temperature
triggers the diffusion of impurities from the bulk of STO, which cause the
creation of off-stoichiometric, dendritic-like SrMoOx islands at the
film/substrate interface. As a valuable workaround, post-deposition annealing
of the LSMO films grown at a relatively-low temperature of about 500
C permits to obtain high-quality epitaxy, atomically-flat surface as
well as a sharp magnetic transition above room temperature and robust
ferromagnetism. Furthermore, under such optimized fabrication conditions
possible scenarios for the formation of the magnetic dead layer as a function
of LSMO film thickness are discussed. Our findings offer effective routes to
finely tailor the complex interplay between structural and magnetic properties
of LSMO thin films via temperature-controlled defect engineering
Rapid Capture of Cancer Extracellular Vesicles by Lipid Patch Microarrays
Extracellular vesicles (EVs) contain various bioactive molecules such as DNA, RNA, and proteins, and play a key role in the regulation of cancer progression. Furthermore, cancer-associated EVs carry specific biomarkers and can be used in liquid biopsy for cancer detection. However, it is still technically challenging and time consuming to detect or isolate cancer-associated EVs from complex biofluids (e.g., blood). Here, a novel EV-capture strategy based on dip-pen nanolithography generated microarrays of supported lipid membranes is presented. These arrays carry specific antibodies recognizing EV- and cancer-specific surface biomarkers, enabling highly selective and efficient capture. Importantly, it is shown that the nucleic acid cargo of captured EVs is retained on the lipid array, providing the potential for downstream analysis. Finally, the feasibility of EV capture from patient sera is demonstrated. The demonstrated platform offers rapid capture, high specificity, and sensitivity, with only a small need in analyte volume and without additional purification steps. The platform is applied in context of cancer-associated EVs, but it can easily be adapted to other diagnostic EV targets by use of corresponding antibodies
On the origin of incoherent magnetic exchange coupling in MnBi/FeCo bilayer system
In this study we investigate the exchange coupling between the hard magnetic
compound MnBi and the soft magnetic alloy FeCo including the interface
structure between the two phases. Exchange spring MnBi-FeCo (x =
0.65 and 0.35) bilayers with various thicknesses of the soft magnetic layer
were deposited onto quartz glass substrates in a DC magnetron sputtering unit
from alloy targets. Magnetic measurements and density functional theory (DFT)
calculations reveal that a Co-rich FeCo layer leads to more coherent exchange
coupling. The optimum soft layer thickness is about 1 nm. In order to take into
account the effect of incoherent interfaces with finite roughness, we have
combined a cross-sectional High Resolution Transmission Electron Microscopy
(HR-TEM) analysis with DFT calculations and micromagnetic simulations. The
experimental results can be consistently described by modeling assuming a
polycrystalline FeCo layer consisting of crystalline (110) and amorphous grains
as confirmed by HR-TEM. The micromagnetic simulations show in general how the
thickness of the FeCo layer and the interface roughness between the hard and
soft magnetic phases both control the effectiveness of exchange coupling in an
exchange spring system
Computation of metallic nanofluid natural convection in a two-dimensional solar enclosure with radiative heat transfer, aspect ratio and volume fraction effects
As a model of nanofluid direct absorber solar collectors (nano-DASCs), the present article describes
recent numerical simulations of steady-state nanofluid natural convection in a two-dimensional
enclosure. Incompressible laminar Newtonian viscous flow is considered with radiative heat transfer.
The ANSYS FLUENT finite volume code (version 19.1) is employed. The enclosure has two adiabatic
walls, one hot (solar receiving) and one colder wall. The Tiwari-Das volume fraction nanofluid model
is used and three different nanoparticles are studied (Copper (Cu), Silver (Ag) and Titanium Oxide
(TiO2)) with water as the base fluid. The solar radiative heat transfer is simulated with the P1 flux and
Rosseland diffusion models. The influence of geometrical aspect ratio and solid volume fraction for
nanofluids is also studied and a wider range is considered than in other studies. Mesh-independence
tests are conducted. Validation with published studies from the literature is included for the copperwater nanofluid case. The P1 model is shown to more accurately predict the actual influence of solar
radiative flux on thermal fluid behaviour compared with Rosseland radiative model. With increasing
Rayleigh number (natural convection i.e. buoyancy effect), significant modification in the thermal flow
characteristics is induced with emergence of a dual structure to the circulation. With increasing aspect
ratio (wider base relative to height of the solar collector geometry) there is a greater thermal convection
pattern around the whole geometry, higher temperatures and the elimination of the cold upper zone
associated with lower aspect ratio. Titanium Oxide nano-particles achieve slightly higher Nusselt
number at the hot wall compared with Silver nano-particles. Thermal performance can be optimized
with careful selection of aspect ratio and nano-particles and this is very beneficial to solar collector
designers