Cluster Phase Transition in Spin Glass Systems and Mechanism of High-Tc Superconductivity

Abstract

We describe here a new mechanism of high-T c (critical temperature) superconductivity. According to our cluster phase transition (CPT) model of spin glass systems, magnetic clusters are present in frustrated magnetic lattices. After giving some details of this model, it is envisaged that in high-T c superconducting cuprate systems, which are magnetically frustrated, these magnetic clusters exist in pairs. The two pair partners are interpenetrating and a spin of one cluster forms a singlet pair with a corresponding spin of the partner cluster. This singlet pairing could occur due to a resonating valence bond (RVB) interaction. The Copper pairs, formed by BCS-Migdal-Eliasberg phonon coupling, interact with the singlet coupled cluster pairs and this interaction is responsible for the T c enhancement and other properties of cuprate superconductors. Consequences of this model and its comparison with other existing theories are also discussed.

Spin glass to superconducting phase transformation by oxidation of a molybdo-cuprate: Mo0.3Cu0.7Sr2TmCu2Oy

“…Furthermore, due to the existence of different magnetic interactions (for instance the Mo V -O-Mo V superexchange interaction is an AFM interaction and the Mo V -O-Cu II superexchange interaction is FM), complex magnetic behaviour is expected. It can also be said that frustration in the 1212 compound can also arise from the Cu-O 5 pyramids [14,34]. Similarly to the case of IrSr 2 (Sm/Eu)Cu 2 O 8 compounds [14] (or Ba 2 PrRuO 6 [35]), instead of the classical individual spin freezing, a cluster-bycluster freezing model could explain the spin glass behaviour of the present material.…”

Antiferromagnetic dipolar ordering in[Co2MnGe∕V]Nmultilayers

“…Returning to history, in the mid 1970s finally the theorists became interested and used some new concepts and models to explain the experimental facts. The spin glasses became very important and gave new impulses to many other fields, such as neural networks, biomolecules and the vortex-glass state in high-T c superconductors [98,102]. While the basic phenomena have been understood qualitatively, a full description by the theory was still lacking.…”