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JOURNALS // Fizika Tverdogo Tela // Archive

Fizika Tverdogo Tela, 2017 Volume 59, Issue 10, Pages 1992–1998 (Mi ftt9433)

This article is cited in 4 papers

Phase transitions

Phase diagram for the $O(n)$ model with defects of “random local field” type and verity of the Imry–Ma theorem

A. A. Berzina, A. I. Morozovb, A. S. Sigova

a Moscow Technological University (MIREA), Moscow, Russia
b Moscow Institute of Physics and Technology (State University), Dolgoprudny, Moscow region

Abstract: It is shown that the Imry–Ma theorem stating that in space dimensions $d<$ 4 the introduction of an arbitrarily small concentration of defects of the “random local field” type in a system with continuous symmetry of the $n$-component vector order parameter ($O(n)$ model) leads to long-range order collapse and to the occurrence of a disordered state is not true if the anisotropic distribution of the defect-induced random local field directions in the space of the order parameter gives rise to the effective anisotropy of the “easy axis” type. In the case of a weakly anisotropic field distribution, in space dimensions 2 $\le d<$ 4 there exists some critical defect concentration, above which the inhomogeneous Imry–Ma state can exist as an equilibrium one. At a lower defect concentration, long-range order takes place in the system. In the case of a strongly anisotropic field distribution, the Imry–Ma state is suppressed completely and long-range order state takes place at any defect concentration.

Received: 10.04.2017

DOI: 10.21883/FTT.2017.10.44970.119


 English version:
Physics of the Solid State, 2017, 59:10, 2016–2022

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