Critical Current Density of As-grown MgB₂ Films Fabricated by Molecular Beam Epitaxy under Low-growth Rate and Low-temperature Conditions

Abstract

As-grown MgB₂ films were grown by MBE (Molecular Beam Epitaxy) apparatus on MgO(100) substrates under low-temperature and low-growth rate conditions using a molecular beam epitaxy. We confirmed the temperature range for MgB₂ fabrication predicted by Liu et al. Under the conditions of substrate temperature 200 °C, B 0.03 nm/s and Mg/B=8, the films were highly c-axis oriented with a superconducting transition of 35 K. We measured the upper critical fields (H_c2) using a 30 T pulsed magnet and critical current density (J_c). H_c2 and J_c at 4.2 K were about 30 T and 10 MA/cm², respectively.