Enhancement of Critical Current in ${\rm Sm}_{1+x}{\rm B}_{2-x}{\rm Cu}_{3}{\rm O}_{y}$ Multilayer Films With the Insertion of Sm-Rich Phase

Coated conductors for power applications require REBCO films with high critical currents (
I

_c
). However, REBCO thick films were likely to be -axis oriented so that was saturated with increasing the film thickness. Previously we reported that Sm-rich (Sm
_1+x
B
_2-x
Cu
₃
O
_y
;
x
= 0.08) films grown at low deposition temperatures on MgO substrates showed the complete
c
-axis orientation and the large terrace width as compared with SmBCO (Sm
_1+x
B
_2-x
Cu
₃
O
_y
;
x
= 0.04 ) films. In this study, we will propose a novel multilayer technique in order to suppress the
a
-axis growth and keep large terrace width. In this technique thin Sm-rich layers are inserted among SmBCO layers. The multilayer structures [Sm - rich/SmBCO]
_*
N (N = 1,2,3...) was fabricated by PLD method on MgO substrates. Although
I

_c
in the SmBCO single layer films at 77 K was saturated at about 350 A/cm-width over the thickness of about 1.3 mum, the SmBCO multilayer films with a thickness of 1.7 mum showed the complete
c
-axis orientation, and the
I

_c
achieved about 800 A/cm-width at 77 K. We confirmed that the growth of the
a
-axis oriented regions was suppressed by the Sm-rich layers. It is considered that the Sm-rich layers act as a template layer for maintaining the
c
-axis orientation, even though the surface temperature decreased with the thickness.