Cubic Anisotropy Created by Defects of "Random Local Anisotropy" Type, and Phase Diagram of the O

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...

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Veröffentlicht in:Physics of the solid state 2017-12, Vol.59 (12), p.2448
Hauptverfasser: Berzin, A.A, Morosov, A.I, Sigov, A.S
Format: Artikel
Sprache:eng
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Zusammenfassung: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 defect-induced 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 [less than or equal to] 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.
ISSN:1063-7834
1090-6460
DOI:10.1134/S1063783417120095