Oxygen ordering at the structural phase transition in Y-Ba-Cu-O

Journal of Applied Physics

1996

mentioning

confidence: 52%

Phase transitions in disordered systems: Exactly solvable model

Journal of Applied Physics

1996

“…For example, physical systems encompassed by this model are, orthorombic high T c superconductors with d-pairing 21 and oxygen ordering near a structural phase transition in Y-Ba-Cu-O. 22 Both RG and the model exhibit similar critical behavior at the phase transition in such systems. The model was also applied successfully in pure systems with coupled order parameters 23 where it derived results such as a fluctuation-induced first-order phase transition, as well as random Ising models 15 where it derived a dimensional reduction.…”

Section: Introductionmentioning

confidence: 99%

Restoration of the continuous phase transition induced by frozen disorder in systems with two interacting order parameters

2004

Phys. Rev. B

A model which in the thermodynamic limit calculates the partition function exactly is used to study the phase transitions of systems with two interacting order parameters coupled to their respective random fields. An ordered phase is always unstable for the spatial range d ഛ 4 when both random fields are present. A continuous phase transition is possible when only one of the random fields is nonzero. For this case, a diagram of the equilibrium order parameter as a function of temperature for three different strengths of the random field is constructed. The critical temperature decreases with increasing randomness. The slope of the order parameter becomes steeper as the random field decreases and diverges as the randomness vanishes. These results can be contrasted with pure systems of coupled parameters where a fluctuation-induced first-order transition occurs.

“…15,16 Renormalization-group theory and the model lead to a similar critical behavior for phase transitions in orthorhombic high-T c superconductors with d pairing 17 and for oxygen ordering near a structural phase transition in Y-Ba-Cu-O. 18 Below we briefly review basic features of the ''pure'' model and derive relationships that will be used in subsequent sections for consideration of the disordered case.…”

mentioning

confidence: 99%

Fluctuation effects in the Ising model with reduced interaction and quenched disorder

1996

Phys. Rev. B

The effect of quenched random fields and local perturbations of critical temperature on the critical behavior at phase transitions is studied within the framework of an exactly solvable model that takes into account interaction of fluctuations with equal and opposite momenta. Using the replica method the dimensional reduction by 2 for systems with finite-range interaction and quenched random fields is explicitly shown. For interaction of the infinite range the model demonstrates the mean-field critical asymptotics independently of dimensionality or the presence of random fields.