Submicron to Nanometer Size Single Particle Measurements

1997 ◽  
Vol 475 ◽  
Author(s):  
B. Barbara ◽  
W. Wernsdorfer ◽  
E. Bonet Orozco ◽  
K. Hasselbach ◽  
A. Benoit ◽  
...  
Keyword(s):  
Magnetization Reversal ◽  
Quantum Tunneling ◽  
Domain Walls ◽  
Switching Field ◽  
Thermally Activated ◽  
Telegraph Noise ◽  
The Mean ◽  
Macroscopic Quantum Tunneling ◽  
20 Nm ◽  
First Time

ABSTRACTLow temperature magnetization measurements of individual ferromagnetic particles and wires are presented (0.1 < T(K) < 6). The detector was a Nb micro-bridge-DC-SQUID, fabricated using electron-beam lithography. The angular dependence of the switching field could be explained approximatively by simple classical micromagnetic concepts (uniform rotation, curling…). However, dynamical measurements evidenced nucleation and propagation of domain walls, except for the smallest particles of about 20 nm. The variation of the mean switching field distribution (as a function of temperature and field sweeping rate) and of the probabilities of switching (as a function of temperature and the applied field) allowed to study in details the dynamics of magnetization reversal of individual particles. For sub-micron particles, we found that above a crossover temperature of 1K, the mean switching field and the switching probability follow a thermally activated model. For temperatures below IK, the dynamics of magnetization reversal becomes temperature independent which is interpreted in terms of deviations from the Néel-Brown model of magnetization reversal due to surface roughness and oxidazation. Although this crossovei temperature is much too large to be interpreted with current models of quantum tunneling, such an effect cannot be excluded. Measurements performed on ferromagnetic nanoparticles of good quality (single crystalline and with a diameter smaller than 25 nm), allowed us to show for the first time that the magnetization reversal can be described by thermal activation over the anisotropy energy barrier, as originally proposed by Néel. The observation of telegraph noise strengthens these results. Our measurements open the door to the observation of macroscopic quantum tunneling oí the magnetization in an individual particle containing 103-105 spins.

EFFECTS OF MACROSCOPIC QUANTUM TUNNELING OF CHARGE IN ULTRASMALL SET DOUBLE-JUNCTIONS WITH EXTERNAL ELECTROMAGNETIC ENVIRONMENT

1993 ◽  
Vol 07 (11) ◽  
pp. 2201-2217 ◽  
Author(s):  
W. KRECH ◽  
A. HÄDICKE
Keyword(s):  
Line Width ◽  
Coulomb Blockade ◽  
Quantum Tunneling ◽  
Higher Order ◽  
Electromagnetic Environment ◽  
Macroscopic Quantum ◽  
High Impedance ◽  
Logarithmic Singularities ◽  
The Mean ◽  
Macroscopic Quantum Tunneling

It is known that classical Coulomb blockade effects of SET devices are disturbed by the tunneling effects of higher order denoted as macroscopic quantum tunneling of charge (q-mqt) or co-tunneling. The influence of an external electromagnetic environment modelled by an additional impedance in the circuit on the mean q-mqt current is studied in the high-impedance limit. This is important especially for devices containing only two SET junctions, for instance the SET electrometer, where the influence of the environment on the Coulomb blockade is remarkable. It can be shown that the Coulomb blockade is only partly destroyed producing a new, lower “quantum” Coulomb blockade. This holds as well in the case of the incoherent as of the coherent q-mqt. Furthermore, a method is presented on how to regularize the logarithmic singularities in the q-mqt current using line width effects.

scholarly journals Macroscopic quantum tunneling of ferromagnetic domain walls

1997 ◽  
Vol 56 (13) ◽  
pp. 8129-8137 ◽  
Author(s):  
Hans-Benjamin Braun ◽  
Jordan Kyriakidis ◽  
Daniel Loss
Keyword(s):  
Quantum Tunneling ◽  
Domain Walls ◽  
Macroscopic Quantum ◽  
Ferromagnetic Domain ◽  
Macroscopic Quantum Tunneling

Micromagnetic Simulation of CoFe Magnetic Nanorings: Switching Behavior in External Magnetic Field

2013 ◽  
Vol 710 ◽  
pp. 80-84 ◽  
Author(s):  
Zhen Gang Guo ◽  
Li Qing Pan ◽  
Hong Mei Qiu ◽  
M. Yasir Rafique ◽  
Shuai Zeng
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Magnetization Reversal ◽  
Domain Walls ◽  
Vortex State ◽  
Switching Behavior ◽  
Switching Field ◽  
Reversal Process ◽  
Magnetic States ◽  
Magnetization Processes

The magnetization reversal processes of magnetic nanorings (Co50Fe50) with different geometric shapes are investigated. In addition to the expected onion and vortex magnetization states, other metastable states are observed in the magnetization processes. We anatomize the formation and transition of magnetic states, and the propagation and annihilation of domain walls in the reversal process through the dynamic picture. Phase diagrams for the magnetization switching behavior depending on the geometric parameters are presented. The simulation shows that the vortex state is stabilized in thick and narrow rings. The switching field from vortex to onion states turns out to increase with thickness and decrease with width and diameter.

Macroscopic quantum tunneling of charge density waves

1999 ◽  
Vol 09 (PR10) ◽  
pp. Pr10-161-Pr10-163
Author(s):  
H. Matsukawa ◽  
H. Miyake ◽  
M. Yumoto ◽  
H. Fukuyama
Keyword(s):  
Charge Density ◽  
Quantum Tunneling ◽  
Charge Density Waves ◽  
Density Waves ◽  
Macroscopic Quantum ◽  
Macroscopic Quantum Tunneling

RESULTS OF INTRALESIONAL TRIAMCINOLONE ACETONIDE FOR CHALAZION TREATMENT

2011 ◽  
pp. 100-104
Author(s):  
Thi Thu Nguyen ◽  
Viet Hien Vo ◽  
Thi Em Do
Keyword(s):  
Success Rate ◽  
Key Words ◽  
Triamcinolone Acetonide ◽  
Lower Eyelid ◽  
Upper Eyelid ◽  
Interventional Trial ◽  
The Mean ◽  
First Time

The study use intralesional triamcinolone acetonide injection proceduce for chalazion treatment.1. Objectives: To evaluate results of intralesional triamcinolone acetonide injection for chalazion treatment. 2. Method: This noncomparative prospective interventional trial included 72 chalazions of 61 patients. 3. Results: 61 patients (72 chalazions) with 19 males (31.1%) và 42 females (68.9%), the mean age was 24 ± 9,78 years. 31.1% patients was the first time chalazion and 68.9% patients was more than one times chalazion including 78.6% patients was recurrent at the first position and 21.4% patients occur at new position. 72 chalazions with 16 (22.2%) chalazions was treated before and 56 (77.8%) chalazions wasn’t done that. 72 chalazions with 49 chalazions (68.1%) are local in upper eyelid and 23 chalazions (31.9%) are local in lower eyelid. The mean of chalazion diameter is 6.99 ± 3.03mm. Intralesional triamcinolone acetonide is injected to treat 72 chalazions with 16 (22.2%) chalazions are injected through the route of skin and 56 (77.8%) chalazions are injected through the route of conjunctiva. After 2 weeks follow-up, the success rate was 93.1% and 6.9% failed. 4. Conclusion: intralesional triamcinolone acetonide injection for chalazion treatment is really effective. Key words: chalazion, intralesional triamcinolone acetonide.

Synthesis of a silymarin-gold nanoparticle conjugate and analysis of its liver-protecting activity

2021 ◽  
Vol 22 ◽  
Author(s):  
Sergey Staroverov ◽  
Sergey Kozlov ◽  
Alexander Fomin ◽  
Konstantib Gabalov ◽  
Alexey Volkov ◽  
...  
Keyword(s):  
Gold Nanoparticles ◽  
Liver Disease ◽  
Carbon Tetrachloride ◽  
Glutathione Depletion ◽  
Laboratory Animals ◽  
Experimental Hepatitis ◽  
Acute Liver Disease ◽  
The Mean ◽  
Extent Of Damage ◽  
First Time

Background: The liver disease problem prompts investigators to search for new methods of liver treatment. Introduction: Silymarin (Sil) protects the liver by reducing the concentration of free radicals and the extent of damage to the cell membranes. A particularly interesting method to increase the bioavailability of Sil is to use synthesized gold nanoparticles (AuNPs) as reagents. The study considered whether it was possible to use the silymarin-AuNP conjugate as a potential liver-protecting drug. Method: AuNPs were conjugated to Sil and examine the liver-protecting activity of the conjugate. Experimental hepatitis and hepatocyte cytolysis after carbon tetrachloride actionwere used as a model system, and the experiments were conducted on laboratory animals. Result: For the first time, silymarin was conjugated to colloidal gold nanoparticles (AuNPs). Electron microscopy showed that the resultant preparations were monodisperse and that the mean conjugate diameter was 18–30 nm ± 0.5 nm (mean diameter of the native nanoparticles, 15 ± 0.5 nm). In experimental hepatitis in mice, conjugate administration interfered with glutathione depletion in hepatocytes in response to carbon tetrachloride was conducive to an increase in energy metabolism, and stimulated the monocyte–macrophage function of the liver. The results were confirmed by the high respiratory activity of the hepatocytes in cell culture. Conclusion: We conclude that the silymarin-AuNP conjugate holds promise as a liver-protecting agent in acute liver disease caused by carbon tetrachloride poisoning.

scholarly journals Subsystem domination influence on magnetization reversal in designed magnetic patterns in ferrimagnetic Tb/Co multilayers

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Łukasz Frąckowiak ◽  
Feliks Stobiecki ◽  
Gabriel David Chaves-O’Flynn ◽  
Maciej Urbaniak ◽  
Marek Schmidt ◽  
...  
Keyword(s):  
Domain Wall ◽  
Magnetization Reversal ◽  
Domain Walls ◽  
Compensation Point ◽  
Relative Sign ◽  
Reversal Process ◽  
Effective Magnetization ◽  
Domain Wall Propagation ◽  
Characteristic Features ◽  
Magnetization Reversal Process

AbstractRecent results showed that the ferrimagnetic compensation point and other characteristic features of Tb/Co ferrimagnetic multilayers can be tailored by He+ ion bombardment. With appropriate choices of the He+ ion dose, we prepared two types of lattices composed of squares with either Tb or Co domination. The magnetization reversal of the first lattice is similar to that seen in ferromagnetic heterostructures consisting of areas with different switching fields. However, in the second lattice, the creation of domains without accompanying domain walls is possible. These domain patterns are particularly stable because they simultaneously lower the demagnetizing energy and the energy associated with the presence of domain walls (exchange and anisotropy). For both lattices, studies of magnetization reversal show that this process takes place by the propagation of the domain walls. If they are not present at the onset, the reversal starts from the nucleation of reversed domains and it is followed by domain wall propagation. The magnetization reversal process does not depend significantly on the relative sign of the effective magnetization in areas separated by domain walls.

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