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▲ [13p-2J-4] Fabrication of highly ordered Co2Fe0.4Mn0.6Si Heusler alloy films on Si and Ge substrate
Keywords:Heusler alloy,Spin injection into semiconductor
Spin injection into semiconductor has been demonstrated by some groups using non-local and/or local Hanle measurements. However, observed spin signal at RT was small because of low spin injection efficiency from ferromagnetic materials to semiconductor. In order to enhance spin signal drastically, Co-based Heusler alloys are particularly promising materials as a spin injector because of its high spin polarization. In order to realize high spin polarization in Hesusler alloys, high atomic ordering in the films is required. In this work, we have systematically investigated structural and magnetic properties in Si(100)- and Ge(100)- subs./MgO/Co2Fe0.4Mn0.6Si Heusler alloy thin films.
Thin films of Co2Fe0.4Mn0.6Si Heusler alloy and MgO tunneling barrier were prepared by magnetron sputtering onto n-doped Si(100) and n-doped Ge(100) substrates in a high vacuum of pressure below 10-6 Pa. Prior to deposition, the substrates were cleaned using HF acid, Semico-clean solution, and then distilled water. Ar pressures during sputtering were about 0.1 Pa for all the prepared films. After deposition, the Co2Fe0.4Mn0.6Si thin films were annealed at various temperatures (Ta). Film thickness of MgO barrier was varied from 0.3 to 2.0 nm and Co2Fe0.4Mn0.6Si films were 30 nm. Very thin Mg layers were inserted into Si/MgO interface to improve crystallinity of MgO tunneling barrier. The structural and magnetic properties were measured by XRD and VSM, respectively. Saturation magnetization of the Si/Mg(0.8)/MgO(2)/Co2Fe0.4Mn0.6Si(30) (in nm) films increased with increasing annealing temperature and maximum value was ca. 1000 emu/cc, which is close to bulk value. In addition, saturation magnetization was drastically improved by inserting thin Mg films. We found by XRD measurements that the improvement of magnetization is due to the improvement of B2 ordering in Co2Fe0.4Mn0.6Si films by inserting thin Mg layer.
Thin films of Co2Fe0.4Mn0.6Si Heusler alloy and MgO tunneling barrier were prepared by magnetron sputtering onto n-doped Si(100) and n-doped Ge(100) substrates in a high vacuum of pressure below 10-6 Pa. Prior to deposition, the substrates were cleaned using HF acid, Semico-clean solution, and then distilled water. Ar pressures during sputtering were about 0.1 Pa for all the prepared films. After deposition, the Co2Fe0.4Mn0.6Si thin films were annealed at various temperatures (Ta). Film thickness of MgO barrier was varied from 0.3 to 2.0 nm and Co2Fe0.4Mn0.6Si films were 30 nm. Very thin Mg layers were inserted into Si/MgO interface to improve crystallinity of MgO tunneling barrier. The structural and magnetic properties were measured by XRD and VSM, respectively. Saturation magnetization of the Si/Mg(0.8)/MgO(2)/Co2Fe0.4Mn0.6Si(30) (in nm) films increased with increasing annealing temperature and maximum value was ca. 1000 emu/cc, which is close to bulk value. In addition, saturation magnetization was drastically improved by inserting thin Mg films. We found by XRD measurements that the improvement of magnetization is due to the improvement of B2 ordering in Co2Fe0.4Mn0.6Si films by inserting thin Mg layer.