Magnetically Defined $B_{\rm irr}$ and $B_{{\rm c}2}$ in $\hbox{BaCeO}_{3}$-Doped $\hbox{YBa}_{2}\hbox{Cu}_{3}\hbox{O}_{6+x} $ Thin Films Grown Under Tensile and Compressive Strain

The effect of lattice mismatch between the film and the substrate on magnetically obtained irreversibility field B
_irr
and upper critical field B
_c2
is investigated in BaCeO
₃
(BCO)-doped YBa
₂
Cu
₃
O
_6+x
(YBCO) thin films prepared by pulsed laser deposition on SrTiO
₃
(STO), SrLaAlO
₄
(SLAO), MgO, and (67%)Pb(Mg
_1/3
Nb
_2/3
)O
₃
-(33%)PbTiO
₃
(PMN-PT) substrates. BCO has been observed to form epitaxially grown, nonelongated, and randomly distributed particles within the whole concentration range of 0-10 wt.%. Therefore, the optimal concentration of 4 wt.% BCO is selected, where the highest J
_c
in the high applied magnetic field range can be observed. The observed flux pinning performance is connected to the structural properties of the films, where substrate-induced uniform strain; crystallographical defects such as dislocations, vacancies, and BCO-nanodot-induced microstrain; low-angle grain boundaries; and YBCO lattice ordering, in general, have substantially different roles at different crystallographical directions.