Nd:YAG-PLD 法による in-situ ポストアニールプロセスを用いた MgB₂ 薄膜の作製

抄録

Magnesium diboride (MgB₂) is a promising candidate for superconducting diodes due to its high lower critical field (H_c1). In this study, we fabricate MgB₂ thin films by a precursor and in-situ post-annealing process as a candidate material for superconducting diodes. The precursor is obtained by pulsed laser deposition (PLD) method using a Nd:YAG laser. The MgB₂ thin films prepared by a high-density Mg-rich target with a ratio of Mg : MgB₂ = 2 : 1 show the highest superconducting transition at T_c^onset = 33.6 K and T_c^zero = 31.7 K. The critical current density J_c(0 T) calculated from magnetization measurements reaches 0.9×10⁶ A/cm² at 20 K. The X-ray diffraction patterns indicate that the MgB₂ phase would be oriented with c-axis perpendicular to the substrate surface and/or would have an extremely fine grain size. These results demonstrate that the precursor and in-situ post-annealing process by Nd:YAG-PLD method is favorable for fabricating superconducting diodes with MgB₂ material.