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JOURNALS // Fizika Tverdogo Tela // Archive

Fizika Tverdogo Tela, 2017 Volume 59, Issue 12, Pages 2420–2424 (Mi ftt9370)

This article is cited in 4 papers

Phase transitions

Cubic anisotropy created by defects of “random local anisotropy” type, and phase diagram of the $O(n)$ model

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

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

Abstract: The expression for the cubic-type-anisotropy constant created by defects of “random local anisotropy” type is derived. 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 anisotropy” type in a system with continuous symmetry of the $n$-component vector order parameter ($O(n)$ model) leads to the long-range order collapse and to occurrence of a disordered state, is not true if an anisotropic distribution of the defectinduced random easy axes directions in the order parameter space creates a global anisotropy of the “easy axis” type. For a weakly anisotropic distribution of the easy axes, in space dimensions 2 $\le d<$ 4 there exists some critical defect concentration, when exceeded, the inhomogeneous Imry–Ma state can exist as an equilibrium one. At the defect concentration lower than the critical one the long-range order takes place in the system. For a strongly anisotropic distribution of the easy axes, the Imry–Ma state is suppressed completely and the long-range order state takes place at any defect concentration.

Received: 23.05.2017

DOI: 10.21883/FTT.2017.12.45243.166


 English version:
Physics of the Solid State, 2017, 59:12, 2448–2452

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