MgB ₂ thin films with high J _c fabricated on Al tape substrates by electron beam evaporation

MgB ₂ thin films on nontextured Al tape substrates were fabricated by electron beam evaporation. MgB ₂ thin film with a boron buffer layer of about 3 nm thickness was also prepared. The thickness of MgB ₂ thin films is 250 nm. The obtained MgB ₂ thin films on Al tape substrates were boron rich in composition and c-axis oriented. The self-field J _c of the MgB ₂ thin film with a boron buffer layer at 10 K and 20 K are 9.45 × 10 ¹⁰ A/m ² and 4.85 × 10 ¹⁰ A/m ², respectively. The magnetic field reduction of J _c in MgB ₂ thin films on Al tape substrates is smaller compared with MgB ₂ wires fabricated by a powder-in-tube method and MgB ₂ thin films fabricated by a hybrid physical chemical vapor deposition method. The field angular dependences of J _c of MgB ₂ thin films on Al tape substrates are similar to that of the MgB ₂ thin film on Si, which was reported previously. This result indicates that grain boundaries act as a dominant pinning center in MgB ₂ thin films on Al tape substrates.