Wagga2026/AC2MP2026

Detecting the half-metallic electronic states in Heusler alloys

Not scheduled

20m

Convention Centre (Charles Sturt University, Wagga Wagga NSW Australia)

Invited Oral Magnetism Magnetism

Speaker

Prof. Rie Umetsu (Tohoku University)

Description

Since half-metallic electronic structures were theoretically predicted in some half-Heusler and full-Heusler alloys, the half-metallic ferromagnets have been intensively investigated in a field of spintronics. Soft X-ray resonant inelastic X-ray scattering (RIXS) and the magnetic circular dichroism (MCD) were performed in order to detect the half-metallic electronic states in Heusler alloys. Because the RIXS is a photon-in/photon-out spectroscopy technique using a high-brilliance synchrotron light source, it allows us to probe the electronic structures in an elemental specific way by tuning the incoming photon energy to the core-level absorption edges. The MCD in the RIXS spectra can probe the spin-polarized electronic structures due to the strong selection rule of the dipole-allowed transition.
The RIXS-MCD measurements were performed at SPring-8 BL07LSU HORNET using left and right circularly polarized light. Single crystals of some Heusler alloys were grown by the Bridgeman method. The crystal orientation was checked using Laue’s back reflection method and the specimen was cut into stripes in the direction parallel to the <100>.
In Mn2VAl and Co2MnSi, it was found that the Zeeman energy, width of the gap formed at the Fermi level, and which spin band opens the half-metallic gap can be revealed from comparison between experimental and theoretical spectra of RIXS-MCD. Furthermore, the RIXS-MCD experiments at the new synchrotron facility in Japan, NanoTerasu, were performed for Co2MnGa alloy, which has been known as a Weyl ferromagnet. Because of the brilliant light at NanoTerasu and the higher resolution of spectra, clearer structures could be observed especially in Co-L edge comparing with the previously obtained spectra at SPring-8. Interestingly, it was found that the Mn-3d orbitals behave half-metallic character around the Fermi level, on the contrary, the Co-3d ones exhibit metallic band character at both spin states. These findings suggest that the Weyl crossing would be caused by the Co-3d electrons.