190 research outputs found
Large inverse tunneling magnetoresistance in CoCrFeAl/MgO/CoFe magnetic tunnel junctions
Magnetic tunnel junctions with the layer sequence
CoCrFeAl/MgO/CoFe were fabricated by magnetron sputtering
at room temperature (RT). The samples exhibit a large inverse tunneling
magnetoresistance (TMR) effect of up to -66% at RT. The largest value of -84%
at 20 K reflects a rather weak influence of temperature. The dependence on the
voltage drop shows an unusual behavior with two almost symmetric peaks at
mV with large inverse TMR ratios and small positive values around zero
bias
Structural and magneto-transport characterization of Co_2Cr_xFe_(1-x)Al Heusler alloy films
We investigate the structure and magneto-transport properties of thin films
of the Co_2Cr_xFe_(1-x)Al full-Heusler compound, which is predicted to be a
half-metal by first-principles theoretical calculations. Thin films are
deposited by magnetron sputtering at room temperature on various substrates in
order to tune the growth from polycrystalline on thermally oxidized Si
substrates to highly textured and even epitaxial on MgO(001) substrates,
respectively. Our Heusler films are magnetically very soft and ferromagnetic
with Curie temperatures up to 630 K. The total magnetic moment is reduced
compared to the theoretical bulk value, but still comparable to values reported
for films grown at elevated temperature. Polycrystalline Heusler films combined
with MgO barriers are incorporated into magnetic tunnel junctions and yield 37%
magnetoresistance at room temperature
Strain-induced insulator state in La_0.7Sr_0.3CoO_3
We report on the observation of a strain-induced insulator state in
ferromagnetic La_0.7Sr_0.3CoO_3 films. Tensile strain above 1% is found to
enhance the resistivity by several orders of magnitude. Reversible strain of
0.15% applied using a piezoelectric substrate triggers huge resistance
modulations, including a change by a factor of 10 in the paramagnetic regime at
300 K. However, below the ferromagnetic ordering temperature, the magnetization
data indicate weak dependence on strain for the spin state of the Co ions. We
interpret the changes observed in the transport properties in terms of a
strain-induced splitting of the Co e_g levels and reduced double exchange,
combined with a percolation-type conduction in an electronic cluster state
Reversible strain effect on the magnetization of LaCoO3 films
The magnetization of ferromagnetic LaCoO3 films grown epitaxially on
piezoelectric substrates has been found to systematically decrease with the
reduction of tensile strain. The magnetization change induced by the reversible
strain variation reveals an increase of the Co magnetic moment with tensile
strain. The biaxial strain dependence of the Curie temperature is estimated to
be below 4K/% in the as-grown tensile strain state of our films. This is in
agreement with results from statically strained films on various substrates
Thickness-dependent Ru exchange spring at La<sub>0.7</sub>Sr<sub>0.3</sub>MnO<sub>3</sub>âSrRuO<sub>3</sub> interface
The conducting oxide ferromagnets SrRuO3 (SRO) and LaSr0.3MnO3 (LSMO) form a Ru exchange spring at a coherent lowâinterdiffusion interface grown on TiO2âterminated SrTiO3(STO)(001) substrates as SRO(d)/LSMO/STO(001) bilayers. Fieldâ and temperatureâdependent magnetization data with systematically varied thickness d of SRO from 7 to 18 unit cells (uc) indicate a thickness of 10â14 uc of the exchange spring which governs magnetic switching and causes thicknessâdependent fieldâcooling effects. Mn L3 edge Xâray magnetic circular dichroism (XMCD) data reveal the dominating inâplane orientation of interfacial spins. In low magnetic fields, noncoplanar, topologically nontrivial spin textures arise and can be switched, driven by the Zeeman energy of the LSMO layer
Anesthesia by electro acupuncture in neurosurgery
Given the fact that in neuroanesthesia the choice of anesthetic substances must take into account the effect they have over the cerebral substance, we felt that using as few drugs as possible eliminates their shortcomings, improving the intraoperative conditions as well as the outcome of the surgical intervention. For this purpose, we have used anesthesia through electro acupunctural stimulation associated to hypnosis, drug relaxation under controlled breathing on a group of 12 patients, from which 10 patients had undergone brain surgery and 2 patients had undergone surgery for herniated disc. The outcomes showed the better effect of this method than that of the classical, the patients showing excellent intraoperative hemodynamic stability, relaxed brain, without the need to use depleted substances, rapid awakening with a much better postoperative analgesia
Implementation of Whole-Body MRI (MY-RADS) within the OPTIMUM/MUKnine multi-centre clinical trial for patients with myeloma.
BACKGROUND: Whole-body (WB) MRI, which includes diffusion-weighted imaging (DWI) and T1-w Dixon, permits sensitive detection of marrow disease in addition to qualitative and quantitative measurements of disease and response to treatment of bone marrow. We report on the first study to embed standardised WB-MRI within a prospective, multi-centre myeloma clinical trial (IMAGIMM trial, sub-study of OPTIMUM/MUKnine) to explore the use of WB-MRI to detect minimal residual disease after treatment. METHODS: The standardised MY-RADS WB-MRI protocol was set up on a local 1.5Â T scanner. An imaging manual describing the MR protocol, quality assurance/control procedures and data transfer was produced and provided to sites. For non-identical scanners (different vendor or magnet strength), site visits from our physics team were organised to support protocol optimisation. The site qualification process included review of phantom and volunteer data acquired at each site and a teleconference to brief the multidisciplinary team. Image quality of initial patients at each site was assessed. RESULTS: WB-MRI was successfully set up at 12 UK sites involving 3 vendor systems and two field strengths. Four main protocols (1.5Â T Siemens, 3Â T Siemens, 1.5Â T Philips and 3Â T GE scanners) were generated. Scanner limitations (hardware and software) and scanning time constraint required protocol modifications for 4 sites. Nevertheless, shared methodology and imaging protocols enabled other centres to obtain images suitable for qualitative and quantitative analysis. CONCLUSIONS: Standardised WB-MRI protocols can be implemented and supported in prospective multi-centre clinical trials. Trial registration NCT03188172 clinicaltrials.gov; registration date 15th June 2017 https://clinicaltrials.gov/ct2/show/study/NCT03188172
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