Absence of discontinuities in ion-channeling parameters forYBa2Cu3O7−δthin films

Abstract

We have measured the ion-channeling minimum yield (${\mathrm{\ensuremath{\chi}}}_{\mathrm{min}}$) and angular width (${\mathrm{\ensuremath{\Psi}}}_{1\mathrm{/}2}$) for Y, Ba, Cu, and O in 2000 \AA{} (001)-oriented films of ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\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 $^{16}\mathrm{O}$(\ensuremath{\alpha},\ensuremath{\alpha}${)}^{16}$O resonance was used to study the O motions. ${\mathrm{\ensuremath{\chi}}}_{\mathrm{min}}$ increases and ${\mathrm{\ensuremath{\Psi}}}_{1\mathrm{/}2}$ 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{\ensuremath{-}}\mathrm{\ensuremath{\delta}}}$ bulk single crystals.