Photoresponse of high Tc superconductor thin films

1992 ◽  
Vol 70 (10-11) ◽  
pp. 1133-1137 ◽  
Author(s):  
F. A. Hegmann ◽  
J. S. Preston
Keyword(s):  
Magnetic Field ◽  
Pulse Width ◽  
Slow Component ◽  
Laser Pulses ◽  
Fast Component ◽  
High Tc ◽  
Small Magnetic Field ◽  
Laser Fluences ◽  
High Laser ◽  
High Laser Fluences

A fast photoresponse is observed in a current-biased epitaxial YBa2Cu3O7 thin-film bridge structure exposed to 100 ps laser pulses. A bolometric response, with a pulse width of the order of 10 ns, dominates at temperatures close to Tc and at high laser fluences. At lower temperatures and fluences, the observed transient response contains distinct fast and slow components. Preliminary results indicate a pulse width for the fast component less than 500 ps. Application of a small magnetic field perpendicular to the sample increases the amplitude of the slow component while leaving the fast component relatively unaffected. Comparison of these results with resistance versus temperature measurements in the same magnetic field suggests that the fast component is nonthermal in origin.

Observations on the Growth of YBa2Cu3O7 Thin Films at Very High Laser Fluences

1995 ◽  
Vol 388 ◽  
Author(s):  
Rand R. Biggers. ◽  
M. Grant Norton ◽  
I. Maartense ◽  
T.L. Peterson ◽  
E. K. Moser ◽  
...  
Keyword(s):  
Thin Films ◽  
Substrate Surface ◽  
Chemical Vapor ◽  
Growth Conditions ◽  
Organic Chemical ◽  
High Fluences ◽  
Laser Fluences ◽  
High Laser ◽  
High Laser Fluences ◽  
Very High

AbstractThe pulsed-laser deposition (PLD) technique utilizes one of the most energetic beams available to form thin films of the superconducting oxide YBa2Cu3O7 (YBCO). IN this study we examine the growth of YBCO at very high laser fluences (25 to 40 J/cm2); a more typical fluence for PLD would be nearer to 3 J/cm2. the use of high fluences leads to unique film microstructures which, in some cases, appear to be related to the correspondingly higher moveabilities of the adatoms. Films grown on vicinal substrates, using high laser fluences, exhibited well-defined elongated granular morphologies (with excellent transition temperature, Tc, and critical current density, Jc). Films grown on vicinal substrates using off-axis magnetron sputtering, plasma-enhanced metal organic chemical vapor deposition (PE-MOCVD), or PLD at more typical laser fluences showed some similar morphologies, but less well-defined. Under certain growth conditions, using high laser fluences with (001) oriented substrates, the YBCO films can exhibit a mixture of a- and c-axis growth where both crystallographic orientations nucleate on the substrate surface at the same time, and grow in concert. the ratio of a-axis oriented to c-axis oriented grains is strongly affected by the pulse repetition rate of the laser.

Synthesis of Magnetite Particles by Pulsed Alexandrite Laser Processing of Metallic Glass Precursors

1995 ◽  
Vol 397 ◽  
Author(s):  
Monica Sorescu ◽  
S.A. Schafer ◽  
E.T. Knobbe
Keyword(s):  
Laser Processing ◽  
Alloy System ◽  
Alexandrite Laser ◽  
Magnetic Texture ◽  
Laser Fluences ◽  
High Laser ◽  
Oxide Phases ◽  
High Laser Fluences ◽  
Magnetite Particles ◽  
Kinetics Of

ABSTRACTSamples of Fe78B13Si9 and Fe81B13.5Si3.5C2 metallic glasses were irradiated with a pulsed alexandrite laser (λ=750 nm, τ=60 μs) using different laser fluences. Kinetics of laser-induced phase transformations and fluence dependence of magnetic properties were studied by scanning electron microscopy (SEM) and Mössbauer spectroscopy. Low laser fluences were found to induce changes in magnetic texture and onset of crystallization. High laser fluences, however, correlated with additional oxidation effects and the formation of stoichiometric Fe3O4 particles in the irradiated alloy system. An activation energy of 11.9 eV was estimated for the laser-driven synthesis of magnetite nanoparticles. Pulsed alexandrite laser processing is an intriguing alternative technique for the controlled synthesis of iron oxide phases from ferromagnetic glass precursors.

scholarly journals Magnetization Switching in the GdFeCo Films with In-Plane Anisotropy via Femtosecond Laser Pulses

Molecules ◽  
2021 ◽  
Vol 26 (21) ◽  
pp. 6406
Author(s):  
Daria O. Ignatyeva ◽  
Pavel O. Kapralov ◽  
Kiran Horabail Prabhakara ◽  
Hiroki Yoshikawa ◽  
Arata Tsukamoto ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Femtosecond Laser ◽  
Laser Pulses ◽  
Femtosecond Laser Pulses ◽  
Metal Alloys ◽  
Magnetization Switching ◽  
Small Magnetic Field ◽  
Plane Anisotropy ◽  
All Optical ◽  
Out Of Plane

Ferrimagnetic rare-earth substituted metal alloys GdFeCo were shown to exhibit the phenomenon of all-optical magnetization switching via femtosecond laser pulses. All-optical magnetization switching has been comprehensively investigated in out-of-plane magnetized GdFeCo films; however, the films with the in-plane magnetic anisotropy have not yet been studied in detail. We report experimental observations of the magnetization switching of in-plane magnetized GdFeCo films by means of the femtosecond laser pulses in the presence of a small magnetic field of about 40 µT. The switching effect has a threshold both in the applied magnetic field and in the light intensity.

scholarly journals Analysis of Direct Optical Ablation and Sequent Thermal Ablation for the Ultrashort Pulsed Laser Photo-Thermal Micromachining

Coatings ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1151
Author(s):  
Chang-Wei Xiong ◽  
Ching-Yen Ho ◽  
Dong-Kai Qiao
Keyword(s):  
Laser Fluence ◽  
Thermal Effects ◽  
Thermal Ablation ◽  
Pulsed Laser ◽  
Processing Quality ◽  
Laser Fluences ◽  
High Laser ◽  
High Laser Fluences ◽  
Ultrashort Pulsed Laser ◽  
Residual Heat

An ultra-fast pulsed laser for materials processing can obtain submicrometer- to nanometer-sized parts or patterns (precision or accuracy) because the heat cannot diffuse in time for an ultra-fast pulsed duration, and this causes a threshold of ablation in multi-photoabsorption. The optical and thermal effects significantly affect the processing quality of an ultrashort pulsed laser for materials. This study utilizes a Laplace transform method to display the optical and thermal effects on the temperature field and the ablated depth of an ultrashort pulsed laser processing of materials. The results reveal that If an ultrafast pulsed laser-induced heat can keep the irradiated region above the evaporated temperature until the thermal diffusion occurs in the lattice of materials, thermal ablation occurs. The optical ablation can get a better processing quality due to less thermal diffusion. This study theoretically elucidates that the depth of optical ablation approximates the product of an optical absorption length and the logarithm of the ratio of laser fluence to laser fluence threshold. It has also been shown that the optical and thermal ablation, respectively, occur in low and high laser fluence because the optical ablation depends directly on the main source of the incident ultrashort pulsed laser. However, the thermal ablation is determined by the residual heat directly from the incident ultrashort pulsed laser after the optical ablation. The increase rate of the ablated depth per pulse with laser fluence is actually lower at high laser fluences than that at low laser fluences because the thermal ablation using the residual heat directly from the incident ultrashort pulsed laser is governed at high laser fluences. This study will provide the closed-form of a solution that elucidate the direct optical ablation and sequent thermal ablation for the ultra-fast pulsed laser photo-thermal processing.

scholarly journals The nature of the ultrafast magnetic phase transition in nickel revealed by correlating EUV-MOKE and ARPES spectroscopies

2019 ◽  
Vol 205 ◽  
pp. 04002
Author(s):  
Zhensheng Tao ◽  
Wenjing You ◽  
Phoebe Tengdin ◽  
Cong Chen ◽  
Xun Shi ◽  
...  
Keyword(s):  
Phase Transition ◽  
Magnetic Phase Transition ◽  
Extreme Ultraviolet ◽  
Magnetic Phase ◽  
Recovery Process ◽  
Time Resolved ◽  
Laser Fluences ◽  
High Laser ◽  
Show Evidence ◽  
High Laser Fluences

By correlating time- and angle-resolved photoemission (Tr-ARPES) and time-resolved transverse- magneto-optical Kerr effect (Tr-TMOKE) measurements, both at extreme ultraviolet (EUV) wavelengths, we uncover the nature of the ultrafast photoinduced magnetic phase transition in Ni. This allows us to explain the ultrafast magnetic response of Ni at all laser fluences - from a small reduction of the magnetization at low laser fluences, to complete quenching at high laser fluences. We provide an alternative explanation to the fluence-dependent recovery timescales commonly observed in ultrafast magneto-optical spectroscopies on ferromagnets: it is due to the bulk-averaging effect and different depths of sample exhibit distinct dynamics, depending on whether a magnetic phase transition is induced. We also show evidence of two competing channels with two distinct timescales in the recovery process, that suggest the presence of coexisting phases in the material.

MICROWAVE ABSORPTION STUDIES ON HIGH-Tc SUPERCONDUCTORS AND RELATED MATERIALS II: Electron Spin Resonance of DPPH Coated on Y1Ba2Cu3Oy as A Probe of Magnetic Field Variations

1991 ◽  
Vol 05 (11) ◽  
pp. 779-787
Author(s):  
K. SUGAWARA ◽  
D.J. BAAR ◽  
Y. SHIOHARA ◽  
S. TANAKA
Keyword(s):  
Magnetic Field ◽  
Temporal Variations ◽  
Zero Field ◽  
High Tc ◽  
Spin Resonance ◽  
Absorption Studies ◽  
Powder Particles ◽  
Increasing Temperature ◽  
Linewidth Broadening ◽  
Magnetic Field Variations

The ESR linewidth (∆H pp ) of DPPH coated on the surface of powder specimens of Y 1 Ba 2 Cu 3 O y has been studied under various magnetic field and temperature conditions. ∆H pp increases substantially with decreasing temperature in the field cooled case, whereas almost no linewidth broadening was found in the zero field cooled case. ∆H pp was found to be sensitive to the applied magnetic field. This effect was very pronounced at temperatures lower than 40 K, but decreased strongly with increasing temperature. The broadening of the resonance lineshape has been attributed to spatial and temporal variations of the fluxon distribution in the powder particles.

V˙o 2 and heart rate kinetics in cycling: transitions from an elevated baseline

2001 ◽  
Vol 90 (6) ◽  
pp. 2081-2087 ◽  
Author(s):  
S. E. Bearden ◽  
R. J. Moffatt
Keyword(s):  
Heart Rate ◽  
Base Excess ◽  
Slow Component ◽  
Lactate Concentration ◽  
Fast Component ◽  
Square Wave ◽  
Mean Response Time ◽  
Rate Kinetics ◽  
Component Amplitude ◽  
Heart Rate Kinetics

The purpose of this study was to examine oxygen consumption (V˙o 2) and heart rate kinetics during moderate and repeated bouts of heavy square-wave cycling from an exercising baseline. Eight healthy, male volunteers performed square-wave bouts of leg ergometry above and below the gas exchange threshold separated by recovery cycling at 35%V˙o 2 peak.V˙o 2 and heart rate kinetics were modeled, after removal of phase I data by use of a biphasic on-kinetics and monoexponential off-kinetics model. Fingertip capillary blood was sampled 45 s before each transition for base excess, HCO[Formula: see text] and lactate concentration, and pH. Base excess and HCO[Formula: see text] concentration were significantly lower, whereas lactate concentration and pH were not different before the second bout. The results confirm earlier reports of a smaller mean response time in the second heavy bout. This was the result of a significantly greater fast-component amplitude and smaller slow-component amplitude with invariant fast-component time constant. A role for local oxygen delivery limitation in heavy exercise transitions with unloaded but not moderate baselines is presented.

scholarly journals Mechanism of retraction of the trailing edge during fibroblast movement.

1981 ◽  
Vol 90 (1) ◽  
pp. 187-200 ◽  
Author(s):  
W T Chen
Keyword(s):  
Slow Component ◽  
Fast Component ◽  
Slow Phase ◽  
Main Body ◽  
Elastic Recoil ◽  
Forward Movement ◽  
Trailing Edge ◽  
Fast Phase ◽  
Focal Contacts

Retraction of the taut, trailing portion of a moving chick heart fibroblast in vitro is an abrupt dynamic process. Upon retraction, the fibroblast tail always ruptures, leaving a small amount of itself attached to the substratum by focal contacts. Time-lapse cinemicrography shows that retraction produces a sudden, massive movement of both surface and cytoplasmic material toward a cluster of focal contacts near the main body of the cell. The appearance of folds on the upper cell surface at this time and the absence of endocytotic vesicles are consistent with this forward movement. Retraction of the trailing edge, either occurring naturally or produced artificially with a microneedle, consists of an initial fast component followed and overlapped by a slow component. Upon artificial detachment in the presence of iodoacetate, dinitrophenol, and sodium fluoride, and at 4 degrees C, the slow component is strongly inhibited and the fast one only slightly inhibited. Moreover of the bundles of microfilaments oriented parallel to the long axis of the tail seen in TEM. Most of the birefringence is lost during the fast phase and the rest during the slow phase of retraction. Concurrently, the bundles of microfilaments disappear during the fast phase of retraction and are replaced by a microfilament meshwork. All of these results are consistent with the hypothesis that the initial fast component of retraction is a passive elastic recoil, associated with the oriented bundles of microfilaments, and that the slow component of retraction is an active contraction, associated with a meshwork of microfilaments.

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