Element-Specific Evaluation of Magnetic Moments in Ferrimagnetic Mn₂VAl Heusler Epitaxial Thin Films

Abstract

  We successfully fabricated L2₁-ordered Mn₂VAl Heusler thin films and evaluated their ferrimagnetic properties by soft x-ray magnetic circular dichroism (XMCD). The buffer layers and annealing temperatures were varied to prepare the Mn₂VAl films. We discovered that Mn₂VAl could be ordered in an L2₁ phase well when it was deposited directly onto an MgO (001) single crystalline substrate. The maximum values of L2₁ and B2 long-range order parameters we obtained were about 0.5 for both phases for samples without a buffer layer, when substrates were heated at 500°C or 600°C. The saturation magnetization (M_s) for these samples was roughly 150 emu/cc. This is rather small compared to that expected from the ideal Slater-Pauling behavior, which might be due to the suppressed degree of L2₁ or B2 ordering. Ferrimagnetism in the Mn₂VAl, ferrimagnetic coupling between Mn and V moments was clearly observed by using the XMCD technique in well-ordered L2₁-Mn₂VAl film as has been predicted in theoretical investigations.