Effect of an Interface Mg Insertion Layer on the Reliability of a Magnetic Tunnel Junction based on a Co2FeAl Full-Heusler Alloy

Abstract

The reliability of a magnetic tunnel junction (MTJ) based on a Co2FeAl (CFA) full-Heusler alloy with a MgO tunnel barrier was evaluated. In particular, the effect of a Mg insertion layer under the MgO was investigated in view of resistance drift by using various voltage stress tests. We compared the resistance change during constant voltage stress (CVS) and confirmed a trap/detrap phenomenon during the interval stress test for samples with and without a Mg insertion layer. The MTJ with a Mg insertion layer showed a relatively small resistance change for the CVS test and a reduced trap/detrap phenomenon for the interval stress test compared to the sample without a Mg insertion layer. This is understood to be caused by the improved crystallinity at the bottom of the CFA/MgO interface due to the Mg insertion layer, which provides a smaller number of trap site during the stress test. As a result, the interface condition of the MgO layer is very important for the reliability of a MTJ using a full-Heusler alloy, and the the insert of a Mg layer at the MgO interface is expected to be an effective method for enhancing the reliability of a MTJ.