scholarly journals Quasi-long-range order in random-anisotropy Heisenberg models

1998 ◽  
Vol 58 (9) ◽  
pp. 5684-5691 ◽  
Author(s):  
Ronald Fisch
Keyword(s):  
Long Range ◽  
Range Order ◽  
Long Range Order ◽  
Random Anisotropy ◽  
Heisenberg Models

scholarly journals QUASI-LONG RANGE ORDER IN GLASS STATES OF IMPURE LIQUID CRYSTALS, MAGNETS, AND SUPERCONDUCTORS

2001 ◽  
Vol 15 (22) ◽  
pp. 2945-2976 ◽  
Author(s):  
D. E. FELDMAN
Keyword(s):  
Liquid Crystals ◽  
Long Range ◽  
Disordered Systems ◽  
Critical Dimension ◽  
Range Order ◽  
Long Range Order ◽  
Weak Disorder ◽  
Random Anisotropy ◽  
Ordered Phases ◽  
Amorphous Magnets

We consider glass states of several disordered systems: vortices in impure superconductors, amorphous magnets, and nematic liquid crystals in random porous media. All these systems can be described by the random-field or random-anisotropy O(N) model. Even arbitrarily weak disorder destroys long range order in the O(N) model. We demonstrate that at weak disorder and low temperatures quasi-long range order emerges. In quasi-long-range-ordered phases the correlation length is infinite and correlation functions obey power dependencies on the distance. In pure systems quasi-long range order is possible only in the lower critical dimension and only in the case of Abelian symmetry. In the presence of disorder this type of ordering turns out to be more common. It exists in a range of dimensions and is not prohibited by non-Abelian symmetries.

Chemical Ordering and Microstructural Affects on Magnetic Properties of Sm2Fe17 and Sm2Fe17Nx

1999 ◽  
Vol 577 ◽  
Author(s):  
B.E. Meacham ◽  
K.W. Dennis ◽  
R.W. Mccallum ◽  
J.E. Shield
Keyword(s):  
Long Range ◽  
Domain Walls ◽  
Antiphase Domain ◽  
Small Degree ◽  
Range Order ◽  
Long Range Order ◽  
Chemical Order ◽  
Chemical Ordering ◽  
Random Anisotropy ◽  
Magnetic Hardness

ABSTRACTThe effect of chemical order and defect structure on the magnetization process in Sm2Fe17 and Sm2Fe17Nx has been investigated. In Sm2Fe17, chemical disorder results in the development of random anisotropy and a small degree of magnetic hardness. The anisotropy is reduced as long-range order increases. The motion of domain walls in Sm2Fe17Nx is more dependent on the antiphase domain structure than on the amount of long-range order.

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