Manifestation of "staircase vortices" in angular dependence of the irreversible boundary of YBaCuO crystals

We report an observation of a double peak in the lossy component of complex susceptibility χ″ in single crystals of YBaCuO. This double peak appears over a finite range of applied dc magnetic fields and intermediated field orientations. We attribute this phenomenon to two components of Jc, which arise from a "staircase vortex" pattern, where portions of the vortex lie between CuO layers. © 1991.