scholarly journals Конкуренция доменных стенок и фазы обратной намагниченности в магнитной релаксации спинового переключателя Pt/Co/Ir/Co/Pt

2018 ◽  
Vol 60 (1) ◽  
pp. 76
Author(s):  
Р.Б. Моргунов ◽  
Г.Л. Львова ◽  
A. Hamadeh ◽  
S. Mangin
Keyword(s):  
Magnetization Reversal ◽  
Magnetic Relaxation ◽  
Domain Walls ◽  
Stable States ◽  
Reverse Magnetization

AbstractA multilayer Pt/Co/Ir/Co/Pt/GaAs heterostructures demonstrates a long term (to several hours) magnetic relaxation between two stable states of the magnetization of the system. The magnetization reversal of the heterostructure layers occurs both due to the formation of nuclei of the reverse magnetization domains and as a result of their further growth by means of motion of domain walls. The competition between two these processes provides a nonexponential character of the magnetic relaxation. At 300 K, the contributions of these processes to the relaxation are commensurable, while, at temperatures lower than 200 K, the contribution of the nucleation is suppressed and the magnetic relaxation occurs as a result of motion of the domain walls.

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.

The effect of Dzyaloshinskii–Moriya interaction on direct and backward transition between magnetic states of Pt/Co/Ir/Co/Pr synthetic ferrimagnet

2021 ◽  
Vol 6 (3) ◽  
pp. 167-178
Author(s):  
Artem D. Talantsev ◽  
Ekaterina I. Kunitsyna ◽  
Roman B. Morgunov
Keyword(s):  
Thin Layer ◽  
Domain Structure ◽  
Magnetization Reversal ◽  
Domain Walls ◽  
Ferromagnetic Layers ◽  
Magneto Optical Kerr Effect ◽  
Magnetic States ◽  
Fluctuation Fields ◽  
Moriya Interaction ◽  
Effect Technique

In this paper, we present the study of domain structure accompanying interstate transitions in Pt/Co/Ir/Co/Pr synthetic ferrimagnet (SF) of 1.1 nm thick and 0.6 – 1.0 nm thin ferromagnetic Co layers. Variation in the thickness of the thin layer causes noticeable changes in the domain structure and mechanism of magnetization reversal revealed by MOKE (Magneto-Optical Kerr Effect) technique. Magnetization reversal includes coherent rotation of magnetization of the ferromagnetic layers, generation of magnetic nuclei, spreading of domain walls (DW), and development of areas similar with strip domains, dependently on thickness of the thin layer. Inequivalence of the direct and backward transitions between magnetic states of SF with parallel and antiparallel magnetizations was observed in sample with thin layer thicknesses 0.8 nm and 1.0 nm. Asymmetry of the transition between these states is expressed in difference fluctuation fields and shapes of reversal magnetization nucleus contributing to the correspondent forward and backward transitions. We proposed simple model based on asymmetry of Dzyaloshinskii–Moriya interaction. This model explains competition between nucleation and domain wall propagation due to increase/decrease of the DW energy dependently on direction of the spin rotation into the DW in respect to external field.

scholarly journals Effects of biological legacies and herbivory on fuels and flammability traits: A long-term experimental study of alternative stable states

2017 ◽  
Vol 105 (5) ◽  
pp. 1309-1322 ◽  
Author(s):  
Melisa Blackhall ◽  
Estela Raffaele ◽  
Juan Paritsis ◽  
Florencia Tiribelli ◽  
Juan M. Morales ◽  
...  
Keyword(s):  
Experimental Study ◽  
Alternative Stable States ◽  
Stable States ◽  
Biological Legacies

Hints for alternative stable states from long-term vegetation dynamics in an unmanaged heathland

2014 ◽  
Vol 26 (2) ◽  
pp. 254-266 ◽  
Author(s):  
Johannes Ransijn ◽  
Sebastian Kepfer-Rojas ◽  
Kris Verheyen ◽  
Torben Riis-Nielsen ◽  
Inger Kappel Schmidt
Keyword(s):  
Vegetation Dynamics ◽  
Alternative Stable States ◽  
Stable States

Long-term pattern of alternative stable states in two shallow eutrophic lakes

1993 ◽  
Vol 30 (1) ◽  
pp. 159-167 ◽  
Author(s):  
IRMGARD BLINDOW ◽  
GUNNAR ANDERSSON ◽  
ANDERS HARGEBY ◽  
STEFAN JOHANSSON
Keyword(s):  
Alternative Stable States ◽  
Stable States ◽  
Eutrophic Lakes

scholarly journals Influence of elastically pinned magnetic domain walls on magnetization reversal in multiferroic heterostructures

2015 ◽  
Vol 92 (5) ◽  
Author(s):  
Arianna Casiraghi ◽  
Teresa Rincón Domínguez ◽  
Stefan Rößler ◽  
Kévin J. A. Franke ◽  
Diego López González ◽  
...  
Keyword(s):  
Magnetization Reversal ◽  
Domain Walls ◽  
Magnetic Domain ◽  
Magnetic Domain Walls ◽  
Multiferroic Heterostructures

scholarly journals Bistable MAP kinase activity: a plausible mechanism contributing to maintenance of late long-term potentiation

2008 ◽  
Vol 294 (2) ◽  
pp. C503-C515 ◽  
Author(s):  
Paul Smolen ◽  
Douglas A. Baxter ◽  
John H. Byrne
Keyword(s):  
Map Kinase ◽  
Dendritic Spine ◽  
Mapk Pathway ◽  
Long Term Potentiation ◽  
Long Term Memory ◽  
Stable States ◽  
Mapk Activity ◽  
Stochastic Fluctuations ◽  
Term Potentiation

Bistability of MAP kinase (MAPK) activity has been suggested to contribute to several cellular processes, including differentiation and long-term synaptic potentiation. A recent model (Markevich NI, Hoek JB, Kholodenko BN. J Cell Biol 164: 353–359, 2004) predicts bistability due to interactions of the kinases and phosphatases in the MAPK pathway, without feedback from MAPK to earlier reactions. Using this model and enzyme concentrations appropriate for neurons, we simulated bistable MAPK activity, but bistability was present only within a relatively narrow range of activity of Raf, the first pathway kinase. Stochastic fluctuations in molecule numbers eliminated bistability for small molecule numbers, such as are expected in the volume of a dendritic spine. However, positive-feedback loops have been posited from MAPK up to Raf activation. One proposed loop in which MAPK directly activates Raf was incorporated into the model. We found that such feedback greatly enhanced the robustness of both stable states of MAPK activity to stochastic fluctuations and to parameter variations. Bistability was robust for molecule numbers plausible for a dendritic spine volume. The upper state of MAPK activity was resistant to inhibition of MEK activation for >1 h, which suggests that inhibitor experiments have not sufficed to rule out a role for persistent MAPK activity in the maintenance of long-term potentiation (LTP). These simulations suggest that persistent MAPK activity and consequent upregulation of translation may contribute to LTP maintenance and to long-term memory. Experiments using a fluorescent MAPK substrate may further test this hypothesis.

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.

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