We have measured the ion-channeling minimum yield (${\mathrm{\chi }}_{\min }$) and angular width (${\mathrm{\Psi }}_{1\mathrm{/}2}$) for Y, Ba, Cu, and O in 2000 Å (001)-oriented films of ${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$ on MgO. The measurements mapped out a 30 K region around the critical temperature (${\mathrm{T}}_{\mathrm{c}}$) in 1–2 K steps, and ${\mathrm{T}}_{\mathrm{c}}$ was determinednin situ. A ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$(α,α${)}^{16}$O resonance was used to study the O motions. ${\mathrm{\chi }}_{\min }$ increases and ${\mathrm{\Psi }}_{1\mathrm{/}2}$ decreases with increasing temperature for all elements, as expected for a smooth increase in vibration amplitude. We see no anomalous jumps in either parameter, which differs from previous reports on ${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$ bulk single crystals.

• Received 22 May 1996

DOI:https://doi.org/10.1103/PhysRevB.55.R700