Fablication of novel spintronic devices using MTJs with magnetic insulators

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In the spintronics research fields, MRAM and STT-RAM have attracted much attention. In the devices, magnetic tunnel junctions (MTJs) are the most impotant elements. The STT-RAM employs the spin torque transfer magnetization reversal to switch the magnetization on very low power. In 2010, Slonczewski proposed that the magnetization is reversed effectively by the spin current generated by spin wave in magnetic insulator. However, the MTJs with magnetic oxide insulator are not reported so far. In this study, we fabricated the epitaxial MgO-MTJs with spinel ferrite oxide using reactive molecular beam epitaxy.From the RHEED and AFM observations, Pt is more appropriate for the insertion layer between Fe and ferrite layers than Cr and Au. Regarding the magnetization process, the saturation field was enhanced by insertion of the non-magnetic layer. The MTJ devices fabricated by e-beam lithography exhibited TMR effects of 70%.