MICROSCOPIC MODEL AND COMPUTER-SIMULATION OF DETWINNING IN YBA2CU3OZ

The results of Monte Carlo simulations of the detwinning of the high-t emperature superconductor YBa2Cu3Oz are reported, To study the effects of detwinning and the concomitant domain growth in this system, a sam ple is first produced having a representative domain structure using a Monte Carlo simulation at fixed temperature and oxygen chemical poten tial based on an asymmetric two-dimensional Ising model. The resulting microstructures typically consist of finely textured orthogonal domai ns indicative of a twinned structure. Next, a symmetry-breaking detwin ning potential is imposed and the time evolution of the system is foll owed. At low temperatures or detwinning potentials only partial detwin ning is typically achieved as the system is often frozen in ''glassy'' domain structures, but at higher temperatures or detwinning potential s complete detwinning is attained. Domain kinetics is mapped out as a function of oxygen chemical potential and temperature and evidence is presented for an algebraic domain growth law of the form t(n) with n b etween 0.33 and 0.75 depending on the control parameters.