Two-dimensional vortex behavior in highly underdoped YBa2Cu3O6+x observed by scanning Hall probe microscopy

J. W. Guikema,1,* Hendrik Bluhm,1 D. A. Bonn,2 Ruixing Liang,2 W. N. Hardy,2 and K. A. Moler1,† 1Department of Physics and Department of Applied Physics, Stanford University, Stanford, California 94305, USA 2Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z1 Received 5 August 2007; revised manuscript received 10 February 2008; published 17 March 2008