研究目的
To determine the element-speci?c density of states (DOS) of half-metallic Co2MnGe using resonant photoelectron spectroscopy at the Co and Mn 2p core absorption edges, and to understand the electronic states near the Fermi level (EF) for future interface design of magnetic tunneling junctions.
研究成果
The study clarified the significant contribution of Mn 3d electrons to the states near the Fermi level in Co2MnGe, with t2g symmetry responsible for electrical conductivity. The Co 3d states exhibit more itinerant character than the Mn 3d states, as indicated by the dominant normal Auger contribution. These findings will assist in the future interface design of magnetic tunneling junctions to overcome temperature-induced reduction of magnetoresistance.
研究不足
The study is limited by the surface sensitivity of the RPES and the presence of partially oxidized Mn at the interface with the Al capping layer, which may affect the accuracy of the DOS near the Fermi level. Additionally, the dominance of the normal Auger process at the Co 2p absorption edge makes it difficult to extract the Co PDOS by taking spectral differences.
1：Experimental Design and Method Selection:
Resonant photoelectron spectroscopy (RPES) was performed at the Co and Mn 2p core absorption edges to determine the element-speci?c DOS. The experiments were conducted at the BL25SU soft x-ray beamline of SPring-8 with an energy resolution of 80 meV. X-ray absorption spectroscopy (XAS) experiments were performed at BL23SU of SPring-8 using the total electron yield method. All measurements were performed at about 40 K.
2：Sample Selection and Data Sources:
A 30-nm-thick Co2MnGe film was prepared by the magnetron sputtering method on a MgO substrate with buffer layers of Cr (10 nm) and Ag (100 nm), and capped with Al (1 nm) to prevent oxidation.
3：List of Experimental Equipment and Materials:
The RPES experiments were performed using soft x-ray synchrotron radiation at SPring-8. The film was characterized by x-ray diffraction and x-ray fluorescence measurements to confirm the L21 ordered phase.
4：The film was characterized by x-ray diffraction and x-ray fluorescence measurements to confirm the L21 ordered phase.
Experimental Procedures and Operational Workflow:
4. Experimental Procedures and Operational Workflow: The valence band spectra were normalized by the sum of the Ge 3d5/2 and 3d3/2 photoelectron intensities. The difference spectrum was produced by subtracting the nonresonant spectrum from the resonant spectrum.
5：Data Analysis Methods:
The obtained valence band spectra were compared with the theoretical partial DOS (PDOS) obtained by first-principles calculation using the WIEN2K program, considering the photoionization cross section and resolution with an energy offset.
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