Asymmetric Field Profile in Bose Glass Phase of Irradiated ${{\mathrm{YBa}}_2{\mathrm{Cu}}_{3}O}_{7-\mathit{\delta }}$: Loss of Interlayer Coherence around $1/3$ of Matching Field

Magneto-optical imaging in ${\mathrm{YBa}}_2{\mathrm{Cu}}_3{\mathrm{O}}_{7-\delta }$ with tilted columnar defects (CD's) shows an asymmetric critical-state field profile. The observed hysteretic shift of the profile ridge (trough) from the center of the sample is explained by in-plane magnetization originating from vortex alignment along CD's. The extracted ratio of the in-plane to out-of-plane magnetization component has a maximum at 1/5 of matching field ( $B_{\Phi }$) and disappears above $B_{\Phi }/3$, suggesting a reduction of interlayer coherence well below $B_{\Phi }$ in the Bose glass phase. Implications are discussed in comparison with the vortex liquid recoupling observed in irradiated ${\mathrm{Bi}}_2{\mathrm{Sr}}_2{\mathrm{CaCu}}_2{\mathrm{O}}_{8+y}$.