Strong, asymmetric flux pinning by miscut-growth-initiated columnar defects in epitaxial YBa[sub 2]Cu[sub 3]O[sub 7[minus][ital x]] films

Strong flux pinning and a pronounced asymmetric angular dependence of [ital J][sub [ital c]]([ital H],[theta]) have been discovered in YBa[sub 2]Cu[sub 3]O[sub 7[minus][ital x]] films grown on miscut, mosaic LaAlO[sub 3] substrate surfaces. A new pinning peak, which at low fields is nearly as strong as the intrinsic pinning,'' is observed for magnetic field orientations between the [ital c] axis and the CuO[sub 2] plane. Cross-section transmission electron microscopy reveals columnar growth defects (2--3 nm diameter) aligned near the [ital c] axis, in concentrations [similar to]10[sup 10] cm[sup [minus]2]. The results demonstrate that deliberately modified substrate surfaces may introduce technologically useful flux pinning in YBa[sub 2]Cu[sub 3]O[sub 7[minus][ital x]] films.