scholarly journals Дальний порядок в двумерных O(n)-моделях, индуцированный случайными полями, и состояние Имри-Ма

2020 ◽  
Vol 62 (2) ◽  
pp. 281
Author(s):  
А.А. Берзин ◽  
А.И. Морозов ◽  
А.С. Сигов
Keyword(s):  
Phase Transition ◽  
Local Field ◽  
Random Fields ◽  
Order Parameter ◽  
Smooth Transition ◽  
Two Dimensional ◽  
Strong Anisotropy ◽  
Continuous Symmetry ◽  
Weak Anisotropy ◽  
Ordered State

A.A. Berzin, A.I. Morosov, and A.S. Sigov The influence of defects of the “random local field” type with an anisotropic distribution of random fields on two-dimensional models with continuous symmetry of the vector order parameter is considered. In the case of weak anisotropy of random fields, with decreasing temperature there takes place a smooth transition from the paramagnetic phase with dynamic fluctuations of the order parameter to the Imry-Ma phase with static fluctuations caused by fluctuations of the random field of defects. In the case of strong anisotropy of random fields, defects lead to an effective decrease in the number of components of the order parameter and the appearance of a phase transition to an ordered state at finite temperature.

scholarly journals Двумерные O(n)-модели с дефектами типа "случайная локальная анизотропия"

2020 ◽  
Vol 62 (4) ◽  
pp. 610
Author(s):  
А.А. Берзин ◽  
А.И. Морозов ◽  
А.С. Сигов
Keyword(s):  
Phase Transition ◽  
Phase Diagram ◽  
Order Parameter ◽  
Easy Axis ◽  
Critical Value ◽  
Smooth Transition ◽  
Two Dimensional ◽  
Continuous Symmetry ◽  
Local Anisotropy ◽  
Ordered State

The phase diagram of two-dimensional systems with continuous symmetry of the vector order parameter containing defects of the “random local anisotropy” type is investigated. In the case of a weakly anisotropic distribution of the easy anisotropy axes in the space of the order parameter, with decreasing temperature, a smooth transition takes place from the paramagnetic phase with dynamic fluctuations of the order parameter to the Imri-Ma phase with its static fluctuations. In the case when the anisotropic distribution of the easy axes induces a global anisotropy of the “easy axis” type that exceeds a critical value, the system goes into the Ising class of universality, and a phase transition to the ordered state occurs in it at a finite temperature.

scholarly journals Посвящается памяти А.И. Морозова Фаза Имри-Ма в системах с дефектами типа "случайное локальное поле" и "случайная локальная анизотропия" (О б з о р)

2022 ◽  
Vol 64 (1) ◽  
pp. 3
Author(s):  
А.А. Берзин ◽  
А.И. Морозов ◽  
А.С. Сигов
Keyword(s):  
Random Field ◽  
Crystallite Size ◽  
Local Field ◽  
Random Fields ◽  
Coercive Field ◽  
Order Parameter ◽  
Large Scale ◽  
Long Range Order ◽  
Local Anisotropy ◽  
Random Anisotropy

The conditions for the appearance in systems with defects of the "random local field" and "random local anisotropy" type of the Imry-Ma phases, in which the direction of the order parameter follows large-scale fluctuations of a random field or random anisotropy, are considered. It is shown that the anisotropy of the distribution of random fields of defects in the space of the order parameter can lead to the appearance of the long-range order. An attention is paid to phase diagrams arising as a result of competition between random fields of defects and anisotropy induced by defects. By the example of a system with random anisotropy (nanocrystalline ferromagnet), the dependences of the coercive field on the crystallite size are considered.

MICROCANONICAL SIMULATIONS OF ELASTIC-DISK SYSTEMS

1994 ◽  
Vol 05 (06) ◽  
pp. 1021-1034 ◽  
Author(s):  
WOLFGANG VERMÖHLEN ◽  
NOBUYASU ITO
Keyword(s):  
Phase Transition ◽  
Order Parameter ◽  
Elastic Moduli ◽  
Md Simulation ◽  
Hard Core ◽  
Effective Density ◽  
Two Dimensional ◽  
Density Reduction ◽  
Elastic Potentials ◽  
Elastic Disk

We performed MD-simulation of two dimensional elastic disks in a microcanonical ensemble and observed the pressure versus the density for the different elastic moduli. As was found in Alder’s simulation, we reconfirmed a plateau in the (pred, ρ*) diagram as an indication for a phase transition with better statistics and observed its dependence on the elastic modulus. This dependence can be explained by the effective density reduction due to the elasticity of the disks. This suggests the universality of the Alder transition of the hard core potential for the contacting elastic potentials. A discussion of a geometrical order parameter |ɸ|2 is included.

Magnetic Properties of Diaquabis(phenoxyacetato)manganese(II) and Related Complexes

1984 ◽  
Vol 39 (4) ◽  
pp. 371-375 ◽  
Author(s):  
Tetsuo Asaji ◽  
Kazumasa Aoki ◽  
Daiyu Nakamura
Keyword(s):  
Phase Transition ◽  
Magnetic Properties ◽  
Magnetic Susceptibility ◽  
Temperature Region ◽  
Magnetic Phase ◽  
Two Dimensional ◽  
Ferromagnetic Interaction ◽  
Magnetic Susceptibilities ◽  
Sharp Maximum ◽  
Ordered State

The magnetic susceptibilities of diaquabis(phenoxyacetato)manganese(II), diaquabis(p-chlorophenoxyacetato) manganese(II), and diaquabis(phenoxyacetato)cobalt(II) were determined in a temperature region below 77 K. The temperature dependence of the magnetic susceptibility observed for the first two manganese(II) complexes shows a broad maximum near 2 K. which can be interpreted as arising from two-dimensional Heisenberg antiferromagnets with S = 5/2. The magnetic susceptibility of the cobalt(II) complex obeys the Curie-Weiss law showing the presence of a ferromagnetic interaction between neighboring cobalt(II) ions. For diaquabis( phenoxyacetato)manganese(II), a magnetic phase transition from a disordered to an antiferromagnetic ordered state was located at 1.633 ± 0.005 K from the sharp maximum of the magnetic susceptibility.

Temperature Effect on the Two-Dimensional Phase Transition Kinetics of Adenine Adsorbed at the Hg Electrode/Aqueous Solution Interface

2003 ◽  
Vol 68 (8) ◽  
pp. 1407-1419 ◽  
Author(s):  
Claudio Fontanesi ◽  
Roberto Andreoli ◽  
Luca Benedetti ◽  
Roberto Giovanardi ◽  
Paolo Ferrarini
Keyword(s):  
Phase Transition ◽  
Aqueous Solution ◽  
Phase Change ◽  
Temperature Effect ◽  
Transition Rate ◽  
Effect Of Temperature ◽  
Two Dimensional ◽  
Solution Interface ◽  
Phase Transition Kinetics ◽  
Kinetics Of

The kinetics of the liquid-like → solid-like 2D phase transition of adenine adsorbed at the Hg/aqueous solution interface is studied. Attention is focused on the effect of temperature on the rate of phase change; an increase in temperature is found to cause a decrease of transition rate.

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