Clusters of Long- $c$ Lattice Phase in ${\rm SmBa}_{2}{\rm Cu}_{3}{\rm O}_{y}$ Films Grown in Low-$P_{{\rm O}2}$ Atmosphere by Pulse Laser Deposition

Phase stability diagram and boundary of
a
- and
c
-axis orientation of SmBa
₂
Cu
₃
O
_y
films grown by pulsed laser deposition were studied. In the study, anomalously long-
c
tetragonal SmBa
₂
Cu
₃
O
_y
were discovered in films grown in low oxygen pressure. The long-
c
phase has 1% longer
c
-axis lattice constant compared to normal-
c
orthorhombic SmBa
₂
Cu
₃
O
_y
and has lower superconducting transition temperature ( ~ 70 K). The long-
c
phase is able to coexist in the normal-
c
matrix over a range of oxygen pressure and growth temperature.