scholarly journals Влияние магнитного поля на фазовые переходы в модели Гейзенберга на треугольной решетке

2021 ◽  
Vol 63 (8) ◽  
pp. 1141
Author(s):  
А.К. Муртазаев ◽  
М.К. Бадиев ◽  
М.К. Рамазанов ◽  
М.А. Магомедов
Keyword(s):  
Magnetic Field ◽  
Phase Transition ◽  
Phase Transitions ◽  
Ground State ◽  
Three Dimensional ◽  
Study Phase ◽  
Histogram Method ◽  
Magnetic Structures ◽  
Wide Range ◽  
The Magnetic Field

The Monte Carlo method was used to study phase transitions, magnetic and thermodynamic properties of the three-dimensional antiferromagnetic Heisenberg model on a layered triangular lattice in a magnetic field. The studies were carried out in the range of variation of the magnetic field value 0≤h≤12. The magnetic structures of the ground state are obtained in a wide range of magnetic field values. The character of phase transitions is determined on the basis of the histogram method of data analysis. It was found that in the range 0≤h≤10, a first-order phase transition is realized. It is shown that a further increase in the magnetic field value removes the degeneracy of the ground state and smears out the phase transition.

SPECTRAL PROPERTIES AND SYMMETRIES OF DOUBLE COVERINGS OF GRAPHS WITH APPLICATIONS TO SUPERCONDUCTIVITY

2005 ◽  
Vol 15 (02) ◽  
pp. 301-324
Author(s):  
JACOB RUBINSTEIN ◽  
MICHELLE SCHATZMAN
Keyword(s):  
Magnetic Field ◽  
Phase Transition ◽  
Phase Transitions ◽  
Ground State ◽  
Spectral Properties ◽  
Embedded Graph ◽  
Symmetry Constraints ◽  
The Laplace Operator ◽  
The Magnetic Field ◽  
Double Coverings

Let M be a planar embedded graph, and let [Formula: see text] be its double covering. We count the multiplicity of the ground states of the Laplace operator on [Formula: see text] under certain symmetry constraints. The examples of interest for us are ladder-like graphs made out of n, identical rectangles. We find that in the case of an odd n, the multiplicity of the ground state is 2, and if n, is even, the ground state is simple. This result gives an answer to a conjecture by Parks on the type of phase transitions that can occur in a superconducting ladder: Parks conjectured that in the case when the magnetic field is one half fluxoid per rectangle, the phase transition would be continuous in the case of a ladder made out of two rectangles. Our result indeed implies Parks conjecture and generalizes it to any even ladder. The mathematics of this paper is a mixture of topology, symmetry arguments and comparison theorem between the eigenvalues of Laplace operators on graphs with well chosen boundary conditions.

scholarly journals Precessing Ball Solitons in Kinetics of a Spin-Flop Phase Transition

2011 ◽  
Vol 2011 ◽  
pp. 1-8 ◽  
Author(s):  
V. V. Nietz
Keyword(s):  
Magnetic Field ◽  
Phase Transition ◽  
Uniaxial Anisotropy ◽  
Precession Frequency ◽  
Initial Condition ◽  
Configuration Energy ◽  
Wide Range ◽  
Kinetics Of ◽  
New Phase ◽  
The Magnetic Field

The fundamentals of precessing ball solitons (PBS), arising as a result of the energy fluctuations during spin-flop phase transition induced by a magnetic field in antiferromagnets with uniaxial anisotropy, are presented. The PBS conditions exist within a wide range of amplitudes and energies, including negative energies relative to an initial condition. For each value of the magnetic field, there exists a precession frequency for which a curve of PBS energy passes through a zero value (in bifurcation point), and hence, in the vicinity of this point the PBS originate with the highest probability. The characteristics of PBS, including the time dependences of configuration, energy, and precession frequency, are considered. As a result of dissipation, the PBS transform into the macroscopic domains of a new phase.

scholarly journals Magnetic Field-Induced Phase Transition

Crystals ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 866
Author(s):  
Yasuhiro H. Matsuda
Keyword(s):  
Magnetic Field ◽  
Phase Transition ◽  
Ground State ◽  
Orbital Motion ◽  
The Magnetic Field

The magnetic field controls the spin and orbital motion of electrons and can induce a phase transition through a change of the ground state [...]

scholarly journals Magnetic structures in a dynamo simulation

1996 ◽  
Vol 306 ◽  
pp. 325-352 ◽  
Author(s):  
A. Brandenburg ◽  
R. L. Jennings ◽  
Å. Nordlund ◽  
M. Rieutord ◽  
R. F. Stein ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Vector Fields ◽  
Magnetic Energy ◽  
Three Dimensional ◽  
Dynamo Action ◽  
Transfer Rates ◽  
Magnetic Structures ◽  
Vorticity Vector ◽  
Early Growth Phase ◽  
The Magnetic Field

We use three-dimensional simulations to study compressible convection in a rotating frame with magnetic fields and overshoot into surrounding stable layers. The, initially weak, magnetic field is amplified and maintained by dynamo action and becomes organized into flux tubes that are wrapped around vortex tubes. We also observe vortex buoyancy which causes upward flows in the cores of extended downdraughts. An analysis of the angles between various vector fields shows that there is a tendency for the magnetic field to be parallel or antiparallel to the vorticity vector, especially when the magnetic field is strong. The magnetic energy spectrum has a short inertial range with a slope compatible with k+1/3 during the early growth phase of the dynamo. During the saturated state the slope is compatible with k−1. A simple analysis based on various characteristic timescales and energy transfer rates highlights important qualitative ideas regarding the energy budget of hydromagnetic dynamos.

scholarly journals Magnetism and the Invisible Man: The mysteries of coronal cavities

2013 ◽  
Vol 8 (S300) ◽  
pp. 139-146 ◽  
Author(s):  
Sarah Gibson
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Interplanetary Space ◽  
Three Dimensional ◽  
Field Measurements ◽  
Coronal Magnetic Field ◽  
Magnetic Structures ◽  
Coronal Magnetic Fields ◽  
Multiple Wavelengths ◽  
The Magnetic Field

AbstractMagnetism defines the complex and dynamic solar corona. Twists and tangles in coronal magnetic fields build up energy and ultimately erupt, hurling plasma into interplanetary space. These coronal mass ejections (CMEs) are transient riders on the ever-outflowing solar wind, which itself possesses a three-dimensional morphology shaped by the global coronal magnetic field. Coronal magnetism is thus at the heart of any understanding of the origins of space weather at the Earth. However, we have historically been limited by the difficulty of directly measuring the magnetic fields of the corona, and have turned to observations of coronal plasma to trace out magnetic structure. This approach is complicated by the fact that plasma temperatures and densities vary among coronal magnetic structures, so that looking at any one wavelength of light only shows part of the picture. In fact, in some regimes it is the lack of plasma that is a significant indicator of the magnetic field. Such a case is the coronal cavity: a dark, elliptical region in which strong and twisted magnetism dwells. I will elucidate these enigmatic features by presenting observations of coronal cavities in multiple wavelengths and from a variety of observing vantages, including unprecedented coronal magnetic field measurements now being obtained by the Coronal Multichannel Polarimeter (CoMP). These observations demonstrate the presence of twisted magnetic fields within cavities, and also provide clues to how and why cavities ultimately erupt as CMEs.

Monte Carlo calculation of the energy parameters and spatial distribution of the cathodic arc ions while passing through the macro-particles filters

2018 ◽  
Vol 1 (1) ◽  
pp. 30-34 ◽  
Author(s):  
Alexey Chernogor ◽  
Igor Blinkov ◽  
Alexey Volkhonskiy
Keyword(s):  
Magnetic Field ◽  
Mass Transfer ◽  
Monte Carlo ◽  
Monte Carlo Calculation ◽  
Inhomogeneous Magnetic Field ◽  
Flow Energy ◽  
Wide Range ◽  
Field Concentrator ◽  
Cathodic Arc ◽  
The Magnetic Field

The flow, energy distribution and concentrations profiles of Ti ions in cathodic arc are studied by test particle Monte Carlo simulations with considering the mass transfer through the macro-particles filters with inhomogeneous magnetic field. The loss of ions due to their deposition on filter walls was calculated as a function of electric current and number of turns in the coil. The magnetic field concentrator that arises in the bending region of the filters leads to increase the loss of the ions component of cathodic arc. The ions loss up to 80 % of their energy resulted by the paired elastic collisions which correspond to the experimental results. The ion fluxes arriving at the surface of the substrates during planetary rotating of them opposite the evaporators mounted to each other at an angle of 120° characterized by the wide range of mutual overlapping.

scholarly journals No-z Model for Magnetic Fields of Different Astrophysical Objects and Stability of the Solutions

Data ◽  
2021 ◽  
Vol 6 (1) ◽  
pp. 4
Author(s):  
Evgeny Mikhailov ◽  
Daniela Boneva ◽  
Maria Pashentseva
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Large Scale ◽  
Point Of View ◽  
Accretion Discs ◽  
Wide Range ◽  
Astrophysical Objects ◽  
Alpha Effect ◽  
The Stability ◽  
The Magnetic Field

A wide range of astrophysical objects, such as the Sun, galaxies, stars, planets, accretion discs etc., have large-scale magnetic fields. Their generation is often based on the dynamo mechanism, which is connected with joint action of the alpha-effect and differential rotation. They compete with the turbulent diffusion. If the dynamo is intensive enough, the magnetic field grows, else it decays. The magnetic field evolution is described by Steenbeck—Krause—Raedler equations, which are quite difficult to be solved. So, for different objects, specific two-dimensional models are used. As for thin discs (this shape corresponds to galaxies and accretion discs), usually, no-z approximation is used. Some of the partial derivatives are changed by the algebraic expressions, and the solenoidality condition is taken into account as well. The field generation is restricted by the equipartition value and saturates if the field becomes comparable with it. From the point of view of mathematical physics, they can be characterized as stable points of the equations. The field can come to these values monotonously or have oscillations. It depends on the type of the stability of these points, whether it is a node or focus. Here, we study the stability of such points and give examples for astrophysical applications.

The role of slow magnetostrophic waves in dipole formation in rapidly rotating dynamos

2021 ◽  
Author(s):  
Aditya Varma ◽  
Binod Sreenivasan
Keyword(s):  
Magnetic Field ◽  
Threshold Value ◽  
Dipole Field ◽  
Wave Frequency ◽  
Alfven Wave ◽  
Inertial Waves ◽  
Axial Dipole ◽  
Wide Range ◽  
The Magnetic Field

<p>It is known that the columnar structures in rapidly rotating convection are affected by the magnetic field in ways that enhance their helicity. This may explain the dominance of the axial dipole in rotating dynamos. Dynamo simulations starting from a small seed magnetic field have shown that the growth of the field is accompanied by the excitation of convection in the energy-containing length scales. Here, this process is studied by examining axial wave motions in the growth phase of the dynamo for a wide range of thermal forcing. In the early stages of evolution where the field is weak, fast inertial waves weakly modified by the magnetic field are abundantly present. As the field strength(measured by the ratio of the Alfven wave to the inertial wave frequency) exceeds a threshold value, slow magnetostrophic waves are spontaneously generated. The excitation of the slow waves coincides with the generation of helicity through columnar motion, and is followed by the formation of the axial dipole from a chaotic, multipolar state. In strongly driven convection, the slow wave frequency is attenuated, causing weakening of the axial dipole intensity. Kinematic dynamo simulations at the same parameters, where only fast inertial waves are present, fail to produce the axial dipole field. The dipole field in planetary dynamos may thus be supported by the helicity from slow magnetostrophic waves.</p>

scholarly journals Magnetic properties of cobalt microwires measured by piezoresistive cantilever magnetometry

2014 ◽  
Vol 1 (1) ◽  
Author(s):  
G. Tosolini ◽  
J. M. Michalik ◽  
R. Córdoba ◽  
J. M. de Teresa ◽  
F. Pérez-Murano ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Room Temperature ◽  
Signal To Noise Ratio ◽  
Static Deflection ◽  
Magnetic Structures ◽  
Dual Beam ◽  
Piezoresistive Cantilevers ◽  
Good Signal ◽  
The Magnetic Field

AbstractWe present the magnetic characterization of cobalt wires grown by focused electron beam-induced deposition (FEBID) and studied using static piezoresistive cantilever magnetometry. We have used previously developed high force sensitive submicron-thick silicon piezoresistive cantilevers. High quality polycrystalline cobalt microwires have been grown by FEBID onto the free end of the cantilevers using dual beam equipment. In the presence of an external magnetic field, the magnetic cobalt wires become magnetized, which leads to the magnetic field dependent static deflection of the cantilevers. We show that the piezoresistive signal from the cantilevers, corresponding to a maximum force of about 1 nN, can be measured as a function of the applied magnetic field with a good signal to noise ratio at room temperature. The results highlight the flexibility of the FEBID technique for the growth of magnetic structures on specific substrates, in this case piezoresistive cantilevers.

Sign in / Sign up

Export Citation Format

Share Document