極薄Ｍｇ層を挿入したＭｇＯ障壁層を用いた磁気トンネル接合に関する評価

Abstract

Magnetic tunnel junctions (MTJs) using an MgO tunnel barrier with ultra-thin Mg insertion layer were studied. It was found that the critical thickness of the MgO barrier layer at which a reasonably high tunneling magnetoresistance (TMR) ratio can be obtained is reduced when an ultra-thin Mg insertion layer is introduced. The highest TMR ratio at a low junction resistance RA was obtained when a 0.4 nm MgO tunnel barrier and a 0.6 nm Mg insertion layer were used. The improvement in the TMR properties is considered to be due to the improvement in the crystallinity of the MgO tunnel barrier with (100) preferred orientation. It was also found that the bias voltage dependence was not affected by insertion of an Mg layer. The present study shows that the use of an ultra-thin Mg insertion layer is effective for improving the TMR ratio in the low RA region, while maintaining the other electrical properties.