SUPPRESSION OF SUPERCONDUCTIVITY IN HYBRID STRUCTURES

2021 ◽  
Vol 0 (1) ◽  
pp. 10-16
Author(s):  
T. KARABASOV ◽  
◽  
A.S. VASENKO ◽  
Keyword(s):  
Critical Temperature ◽  
Topological Insulator ◽  
High Surface ◽  
Ferromagnetic Layer ◽  
The Body ◽  
Hybrid Nanostructures ◽  
Hybrid Structures ◽  
Quantum Calculations ◽  
Superconducting Transition ◽  
Superconducting Layer

Materials that possess strong spin-orbit interaction have provoked great interest over the past few years, in particular, in the actively developing field of quantum calculations. A topological insulator is a good example of such a material. The topological insulator has high surface conductivity, whereas in the body it shows the properties of an insulator, this being a purely phenomenological definition of a substance. Superconducting hybrid structures also present a promising elemental basis for quantum calculations and spintronics. This paper considers hybrid nanostructures like superconductor/ ferromagnet/ superconductor (S/F/S) and superconductor/ topological insulator/ superconductor (S/TI/S), where a uniform magnetic field is imposed onto the surface of the topological insulator. The paper investigates the behaviour of critical temperature in the superconducting layer Тс depending on different parameters of the systems, in particular, the dependence of Тс on the thickness of the layer dn in the topological insulator TI (or the ferromagnetic layer F). To solve the problem, we use the formalism of the quasiclassical Green's functions . The model assumes a diffusion mode, which holds true when the electron free path length is much less than the characteristic scale of the system. As a rule, such a limit is easier to be performed, since the commonly made structures have admixtures. To solve the problem on self-consistency of the superconducting energetic slot D we use a unimode approximation. As the results of our calculations, we give curves of the critical temperature behaviour in the systems under consideration. It is demonstrated that while the critical temperature exhibits a nonmonotonic behaviour and can make oscillations because of phase 0 -p transitions in the S/F/S structures, in the S/TI/S structures the temperature of the superconducting transition exhibits a trivial behaviour characterized by the monotonic attenuation.

scholarly journals Structural, Superconducting and Magnetic Properties of La3-XRxNi2B2N3-δ with R = Ce, Pr, Nd

2011 ◽  
Vol 170 ◽  
pp. 165-169 ◽  
Author(s):  
Tahir Ali ◽  
Ernst Bauer ◽  
Gerfried Hilscher ◽  
Herwig Michor
Keyword(s):  
Magnetic Properties ◽  
Structure Type ◽  
The Body ◽  
Spin Reorientation ◽  
Superconducting Transition ◽  
X Ray Diffraction ◽  
Range Magnetic Order ◽  
Long Range Magnetic Order ◽  
First Time ◽  
Magnetic Pair

We report on structural and superconducting properties of La3-xRxNi2B2N3- where La is substituted by the magnetic rare-earth elements Ce, Pr, Nd. The compounds Pr3Ni2B2N3- and Nd3Ni2B2N3- are characterized for the first time. Powder X-ray diffraction confirmed all samples R3Ni2B2N3- with R = La, Ce, Pr, Nd and their solid solutions to crystallize in the body centered tetragonal La3Ni2B2N3 structure type. Superconducting and magnetic properties of La3-xRxNi2B2N3- were studied by resistivity, specific heat and susceptibility measurements. While La3Ni2B2N3- has a superconducting transition temperature Tc ~ 14 K, substitution of La by Ce, Pr, and Nd leads to magnetic pair breaking and, thus, to a gradual suppression of superconductivity. Pr3Ni2B2N3- exibits no long range magnetic order down to 2 K, Nd3Ni2B2N3- shows ferrimagnetic ordering below TC =17 K and a spin reorientation transition to a nearly antiferromagnetic state at 10 K.

The Permeability and Structure of the Cuticle of the Aquatic Larva of Sialis Lutaria

1955 ◽  
Vol 32 (2) ◽  
pp. 330-352 ◽  
Author(s):  
J. SHAW
Keyword(s):  
Body Weight ◽  
Critical Temperature ◽  
Heavy Water ◽  
Sudden Change ◽  
Indirect Evidence ◽  
The Body ◽  
Permeability Constant ◽  
Water Influx ◽  
Terrestrial Insects ◽  
Aquatic Larva

1. The permeability to water of the cuticle of Sialis larvae has been measured, using heavy water as tracer. The penetration was slow, the permeability constant being only 1.8 x 10-2 cm./hr. at 20° C. There was no obvious difference between the rate of water influx and outflux. The rate at which water penetrated into the tissues from the blood was much greater than through the cuticle. The Q10 for diffusion through the body surface was high, lying between 3.0 and 3.8. The osmotic uptake of water was calculated to be about 1% of the body weight per day at 10° C. 2. Drinking of water did not occur in normal larvae, but in larvae with the blood volume reduced, osmotic uptake of water through the gut did take place and the gut wall was much more permeable to water than the cuticle. A similar intake of water probably occurred during moulting. 3. The permeability of the cuticle to chloride was measured and also found to be of a low order (P = 1.04 x 10-4 cm./hr. at 17° C.). Sodium diffused out of the larva at the same rate as the chloride. 4. Histological examination of the cuticle showed that in the abdomen it was thin and consisted of a 7µ. thick endocuticle and a 1 µ epicuticle. Over the thorax it was thicker, and a polyphenol layer was present as the outer layer of the epicuticle. There was indirect evidence of the presence of a wax layer. 5. Wax was extracted from the cuticle, and the thickness of the layer from which it was derived was estimated by means of a monolayer technique. In the cuticle of the abdomen and gills the thickness averaged 0.1 µ. 6. The permeability to water of the cuticle was compared with that of terrestrial insects and was found to be much greater. This difference was not due to the thickness of the wax layer but probably to some physical properties of the wax. The cuticle of Sialis larvae showed no ‘critical temperature’ or sudden change in the permeability properties with temperature over the range of temperatures studied.

scholarly journals Proximity effect in [Nb(1.5 nm)/Fe(x)]10/Nb(50 nm) superconductor/ferromagnet heterostructures

2020 ◽  
Vol 11 ◽  
pp. 1254-1263
Author(s):  
Yury Khaydukov ◽  
Sabine Pütter ◽  
Laura Guasco ◽  
Roman Morari ◽  
Gideok Kim ◽  
...  
Keyword(s):  
Intermediate State ◽  
Proximity Effect ◽  
Intermediate Phase ◽  
Ferromagnetic Layer ◽  
Residual Resistivity ◽  
Neutron Reflectometry ◽  
Superconducting Transition ◽  
Residual Resistivity Ratio ◽  
Resistivity Ratio ◽  
Weak Ferromagnetic

We have investigated the structural, magnetic and superconduction properties of [Nb(1.5 nm)/Fe(x)]10 superlattices deposited on a thick Nb(50 nm) layer. Our investigation showed that the Nb(50 nm) layer grows epitaxially at 800 °C on the Al2O3(1−102) substrate. Samples grown at this condition possess a high residual resistivity ratio of 15–20. By using neutron reflectometry we show that Fe/Nb superlattices with x < 4 nm form a depth-modulated FeNb alloy with concentration of iron varying between 60% and 90%. This alloy has weak ferromagnetic properties. The proximity of this weak ferromagnetic layer to a thick superconductor leads to an intermediate phase that is characterized by a suppressed but still finite resistance of structure in a temperature interval of about 1 K below the superconducting transition of thick Nb. By increasing the thickness of the Fe layer to x = 4 nm the intermediate phase disappears. We attribute the intermediate state to proximity induced non-homogeneous superconductivity in the structure.

Magnetic Properties

2003 ◽  
Author(s):  
Toshiaki Enoki ◽  
Morinobu Endo ◽  
Masatsugu Suzuki
Keyword(s):  
Critical Temperature ◽  
Exchange Interaction ◽  
Three Dimensional ◽  
Ferromagnetic Layer ◽  
Magnetic Behavior ◽  
Interlayer Coupling ◽  
Spin Correlation ◽  
Layered Compounds ◽  
Metal Chlorides ◽  
Spin Order

Two-dimensional (2D) magnetic phase transition has been one of the major topics of condensed matter physics. There are many materials in which the magnetic ions are arranged in planes so that there is strong coupling between the spins within a plane, but only a weak coupling between spins in different planes. In materials such as transition metal chlorides (FeCl2, CoCl2, and NiCl2) there is a strong ferromagnetic coupling within the planes and a coupling between planes which is weaker by a factor of 10 or so and antiferromagnetic. In more complicated ferromagnetic layer compounds such as (CH3 NH3)2 CuCl4, the interlayer coupling is down by a factor of more than a thousand. There are also many materials, such as Rb2MnF4, Rb2CoF4, and K2CoF4, in which the coupling within the plane is antiferromagnetic. This can result in a very much reduced coupling between the planes, since one spin may have four spins in the next plane which are at an equal distance, and their effects cancel out. As a result, the coupling between layers in this material is down by a factor of 106. In these layered compounds the magnetic behavior is only 2D-like at a certain distance away from the critical temperature. Close to the critical temperature, there is a long-range correlation of the spins within the layer and such a correlated region will interact between one layer and the next even if the coupling between individual spins is weak, since many spins can contribute coherently. Thus the spin order near the critical temperature is essentially three-dimensional (3D). What condition should be required for the occurrence of a real 2D spin order in layered magnetic systems? We consider a system consisting of only two magnetic layers separated by a distance. The effective interplanar exchange interaction J'eff is given by J'(ξa)2, but not by J', where ξa is the in-plane spin correlation length and J' is the interplanar exchange interaction. If ξa diverges on approaching a critical temperature, the effective interplanar exchange interaction J'eff becomes comparable with the intraplanar exchange interaction J.

Scaling of Resistivities in MgB2

2006 ◽  
Vol 47 ◽  
pp. 113-117
Author(s):  
Petr Vašek
Keyword(s):  
Magnetic Field ◽  
Thin Films ◽  
Critical Temperature ◽  
External Magnetic Field ◽  
Transport Current ◽  
Zero Magnetic Field ◽  
Superconducting Transition ◽  
Hall Voltage ◽  
Transition Range ◽  
Width Of Superconducting Transition

Longitudinal and transverse voltages have been measured on thin films of MgB2 with different width of superconducting transition range. The study has been performed in zero and nonzero external magnetic fields. The non-zero transverse voltage has been observed in close vicinity of the critical temperature in zero external magnetic field while far enough from Tc this voltage has been zero. In magnetic field it merges into transverse voltage which is an even function with respect to the direction of the field. Usual Hall voltage starts to appear with increasing magnetic field. At the highest field the even voltage disappears and only the Hall voltage is measurable i.e. the transverse even voltage is suppressed with increasing magnetic field and increasing transport current as well. New scaling between transverse and longitudinal resistivities has been observed in the form ρxy~dρxx/dT . This correlation is valid not only in the zero magnetic field but also in nonzero magnetic field where transverse even voltage can be detected. Several models trying to explain observed results are discussed. The most promising seems to be guided motion of the vortices.

scholarly journals Finite-size effects in metallic superlattice systems

1995 ◽  
Vol 73 (9-10) ◽  
pp. 545-553
Author(s):  
J. Chen ◽  
R. Kobes ◽  
J. Wang
Keyword(s):  
Critical Temperature ◽  
Simple Model ◽  
Proximity Effect ◽  
Size Effects ◽  
Finite Size ◽  
Cooper Pairs ◽  
Superconducting Layer ◽  
Finite Size Effects ◽  
Realistic Form ◽  
Pair Amplitude

Clean metallic superlattice systems composed of alternating layers of superconducting and normal materials are considered, particularly aspects of the proximity effect as it affects the critical temperature. A simple model is used to address the question of when a finite–sized system theoretically approximates well a true infinite superlattice. The methods used in the analysis afford some tests of the approximation used that the pair amplitude of the Cooper pairs is constant over a superconducting region. We also use these methods to construct a model of a single superconducting layer which intends to incorporate a more realistic form of the pair amplitude than a simple constant.

scholarly journals Recommendations for Nanomedicine Human Subjects Research Oversight: An Evolutionary Approach for an Emerging Field

2012 ◽  
Vol 40 (4) ◽  
pp. 716-750 ◽  
Author(s):  
Leili Fatehi ◽  
Susan M. Wolf ◽  
Jeffrey McCullough ◽  
Ralph Hall ◽  
Frances Lawrenz ◽  
...  
Keyword(s):  
Medical Devices ◽  
Human Subjects ◽  
High Surface ◽  
The Body ◽  
Biologically Active ◽  
Implantable Medical Devices ◽  
Research Oversight ◽  
Insoluble Drugs ◽  
Drug Eluting

Nanomedicine is yielding new and improved treatments and diagnostics for a range of diseases and disorders. Nanomedicine applications incorporate materials and components with nanoscale dimensions (often defined as 1-100 nm, but sometimes defined to include dimensions up to 1000 nm, as discussed further below) where novel physiochemical properties emerge as a result of size-dependent phenomena and high surface-to-mass ratio. Nanotherapeutics and in vivo nanodiagnostics are a subset of nanomedicine products that enter the human body. These include drugs, biological products (biologics), implantable medical devices, and combination products that are designed to function in the body in ways unachievable at larger scales. Nanotherapeutics and in vivo nanodiagnostics incorporate materials that are engineered at the nanoscale to express novel properties that are medicinally useful. These nanomedicine applications can also contain nanomaterials that are biologically active, producing interactions that depend on biological triggers. Examples include nanoscale formulations of insoluble drugs to improve bioavailability and pharmacokinetics, drugs encapsulated in hollow nanoparticles with the ability to target and cross cellular and tissue membranes (including the bloodbrain barrier) and to release their payload at a specific time or location, imaging agents that demonstrate novel optical properties to aid in locating micrometastases, and antimicrobial and drug-eluting components or coatings of implantable medical devices such as stents.

Research on the Near-Net Forging Processes for the Body of Overrunning Clutch

2015 ◽  
Vol 727-728 ◽  
pp. 396-402
Author(s):  
Tai Bin Wu
Keyword(s):  
Energy Saving ◽  
Economic Benefit ◽  
High Surface ◽  
The Body ◽  
Die Design ◽  
Cold Extrusion ◽  
High Surface Quality ◽  
Forging Process ◽  
Forging Press ◽  
Material Saving

The near-net forging processes for the body of overrunning clutch was studied by adopting the warm upsetting,warm no-flash die forging,cold extrusion and cold coining process。The arrangement of the near-net forging processes,the procedure of the near-net forging process,the choice of forging press,the structures of the punch and the lower die,and the key problem of die design were introduced in detail。The chief advantages of this process include the high surface quality,closer tolerances and qualified inner avity for the body of overrunning clutch without subsequent machining;so it is significantly energy-saving,material-saving,and the economic benefit is remarkable。

scholarly journals Growth of GaN@InGaN Core-Shell and Au-GaN Hybrid Nanostructures for Energy Applications

2009 ◽  
Vol 2009 ◽  
pp. 1-6 ◽  
Author(s):  
Tevye Kuykendall ◽  
Shaul Aloni ◽  
Ilan Jen-La Plante ◽  
Taleb Mokari
Keyword(s):  
Rational Design ◽  
Chemical Vapor ◽  
Hybrid Nanostructures ◽  
Engineering Properties ◽  
Hybrid Structures ◽  
Organic Chemical ◽  
Bandgap Energy ◽  
Core Shell ◽  
X Ray ◽  
Gan Nanowires

We demonstrated a method to control the bandgap energy of GaN nanowires by forming GaN@InGaN core-shell hybrid structures using metal organic chemical vapor deposition (MOCVD). Furthermore, we show the growth of Au nanoparticles on the surface of GaN nanowires in solution at room temperature. The work shown here is a first step toward engineering properties that are crucial for the rational design and synthesis of a new class of photocatalytic materials. The hybrid structures were characterized by various techniques, including photoluminescence (PL), energy dispersive x-ray spectroscopy (EDS), transmission and scanning electron microscopy (TEM and SEM), and x-ray diffraction (XRD).

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