Large magnetoresistance in Heusler-alloy-based epitaxial magnetic junctions with semiconducting Cu(In0.8Ga0.2)Se2 spacer

Abstract

We investigated the structure and magneto-transport properties of magnetic junctions using a Co 2 Fe(Ga 0.5 Ge 0.5) Heusler alloy as ferromagnetic electrodes and a Cu(In 0.8 Ga 0.2)Se 2 (CIGS) semiconductor as spacers. Owing to the semiconducting nature of the CIGS spacer, large magnetoresistance (MR) ratios of 40% at room temperature and 100% at 8 K were obtained for low resistance-area product (RA) values between 0.3 and 3 X lm 2. Transmission electron microscopy observations confirmed the fully epitaxial growth of the chalcopyrite CIGS layer, and the temperature dependence of RA indicated that the large MR was due to spin dependent tunneling.

Effect of MgO Underlying Layer on the Growth of GaOx Tunnel Barrier in Epitaxial Fe/GaOx/(MgO)/Fe Magnetic Tunnel Junction Structure

“…Thanks to the coherent spin-polarized tunneling, the observed MR ratio is several times higher than those reported in MTJs consisting of polycrystalline FM electrodes with an amorphous GaO x barrier (at most ~22% at RT) [22,23,24]. This is the highest value among the reported MTJs with a SC barrier at RT [14,15,22,23,24,25,26,27,28,29,30,31]. It was found in the fully epitaxial MTJs that the growth of a few monoatomic (ML; 1 ML = 0.21 nm) MgO(001) underlying layers on the Fe(001) bottom electrode are indispensable to realize a high MR ratio and that a tunneling MR (TMR) effect cannot be observed without the MgO underlying layer.…”

“…Semiconductors (SC) have great potential as the tunnel-barrier of MTJ for a low resistance-area product [14,15] because of its rather narrow band-gap, compared with insulators. Also, fully single-crystalline FM/SC/FM structure is one of the important building blocks of a vertical-type spin field-effect-transistor having nonvolatile memory functionality [16,17,18,19].…”

Theoretical Study on Magnetic Tunneling Junctions with Semiconductor Barriers CuInSe₂ and CuGaSe₂ Including a Detailed Analysis of Band-Resolved Transmittances

“…In our previous work 9) , we theoretically studied spin-dependent transport properties of two MTJs with different semiconductor barriers, CuInSe2 (CIS) and CuGaSe2 (CGS), to understand the origin of the high MR ratios observed in the CIGS-based MTJs 8) . By analyzing their complex band structures and k// dependences of the transmittances, we found that spin-dependent coherent transport of Δ1 wave functions occurs in both the CIS-and CGS-based MTJs, which can explain the high MR ratios in the CIGS-based MTJs.…”

Three-dimensional integration technology of magnetic tunnel junctions for magnetoresistive random access memory application

“…1) New tunnel-barrier materials, such as spinel Mg-Al-O(001), and new ferromagnetic materials, such as Heusler alloys, [12][13][14][15][16][17] may outperform the MgO barrier and CoFeB electrodes in the near future. For an MTJ composed of such new materials to exhibit high performance, it must be epitaxially grown on a single-crystal substrate.…”