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Two-Dimensional Melting of Magnetic Bubble Arrays: A Continuous Hexatic-To-Liquid Transition

Published online by Cambridge University Press:  25 February 2011

R. Seshadri  and
R. M. Westervelt
R. Seshadri
Affiliation:
Division of Applied Sciences and Department of PhysicsHarvard University, Cambridge, MA 02138
R. M. Westervelt
Affiliation:
Division of Applied Sciences and Department of PhysicsHarvard University, Cambridge, MA 02138
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Abstract

Arrays of two-dimensional magnetic bubbles in thin garnet films undergo a hexatic-toliquid transition as a function of bubble density controlled by an applied spatially uniform dc bias magnetic field that opposes the magnetization in the bubbles. The phase transition is driven by topological point defects. The bubbles are observed directly using optical microscopy and digital imaging techniques. In the presence of a linear gradient in the dc bias magnetic field the hexatic-to-liquid transition occurs spatially in the direction of the gradient. As the system goes from hexatic to liquid, a continuous decrease in bubble density accompanied by a continuous disordering of the array is observed along the gradient direction. This continuous disordering persists even after the system is allowed to equilibrate for very long periods of time, indicating that the hexatic-to-liquid transition is continuous at equilibrium. Dynamics of topological defects observed in the gradient field correspond to those observed in the uniform field.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 248: Symposium O – Complex Fluids , 1991 , 35
Copyright
Copyright © Materials Research Society 1992

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