Enhancement of critical current in Sm_1+xB_2-xCu ₃O_y multilayer films with the insertion of Sms-rich phase

Coated conductors for power applications require REBCO films with high critical currents (I_c). However, REBCO thick films were likely to be a-axis oriented so that I_c was saturated with increasing the film thickness. Previously we reported that Sm-rich (Sm_1+xBa _2-xCu₃O_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+xBa _2-xCu₃O_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 μm, the SmBCO multilayer films with a thickness of 1.7 μm 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.