Evidence for localized moment picture in Mn-based Heusler compounds

Abstract

X-ray absorption spectroscopy (XAS) and X-ray magnetic circular dichroism (XMCD) were used to probe the oxidation state and element specific magnetic moments of Mn in Heusler compounds with different crystallographic structure.The results were compared with theoretical calculations, and it was found that in full Heusler alloys, Mn is metallic (oxidation state near 0) on both sublattices. The magnetic moment is large and localized when octahedrally coordinated by the main group element, consistent with previous theoretical work, and reduced when the main group coordination is tetrahedral. By contrast, in the half Heusler compounds the magnetic moment of the Mn atoms is large and the oxidation state is +1 or +2. The magnetic and electronic properties of Mn in full and half Heusler compounds are strongly dependent on the structure and sublattice, a fact that can be exploited to design new materials.

Electronic structure and magnetic properties of the half-metallic ferrimagnetMn2VAlprobed by soft x-ray spectroscopies

“…Figure 4(a) displays the enlarged view of the Mn L 2,3 XAS spectrum of Mn 2 VAl, showing a metallic line shape as reported in Ref. 22. Compared with the XAS spectrum of Co 2 MnSi, in which the Mn 3d states have a localized 3d 5 character [13,14,17], the L 3 main line of Mn 2 VAl shifts to higher energies even though the leading edges start at the same energy of 638 eV.…”

“…The electronic structure of Co 2 MnSi has been known as the Co 3d electrons are itinerant, while the Mn 3d electrons contribute to the local magnetic moment [13,14,17]. Nevertheless, only few works have been performed on Mn 2 VAl [20][21][22] because of the difficulty in synthesizing high quality crystals. It has been reported as the epitaxially grown Mn 2 VAl films are prone to various disorder [20].…”

“…It has been reported as the epitaxially grown Mn 2 VAl films are prone to various disorder [20]. Since the disorder effects change the magnetic properties and the local electronic structure [21], the line shapes of XAS and XMCD spectra varied depending on the individual samples [20][21][22]. Therefore, the electronic structure of Mn 2 VAl is still controversial.…”

Redox Metal–Ligand Cooperativity Enables Robust and Efficient Water Oxidation Catalysis at Neutral pH with Macrocyclic Copper Complexes

“…91 The presence of redox active ancillary ligands that can be reversibly oxidized allows to have an additional site of oxidative equivalent storage and thus increases the versatility for catalyst design that in turn can lead to better control of overpotentials as well as turnover frequencies. This is particularly important for 1 st row TM where the energy differences from successive oxidation states is much larger than in Ru complexes as manifested by their K-edge energies (0.8 eV per oxidation state for Ru; 92 2.8-3.3 eV for Cr, Mn, Co; 93,94,95 and 3.1 eV for Cu (this work)). The ligand design is also important with regard to the stability of these complexes at low pH.…”

IrCrMnZ (Z=Al, Ga, Si, Ge) Heusler alloys as electrode materials for MgO-based magnetic tunneling junctions: A first-principles study

“…Z atom), the magnetic moment of Mn is largely localized and for tetrahedrally coordinated case it has itinerant type of magnetism. [42] For the IrCrMnZ systems, Mn has octahedral coordination and on the other hand Cr has tetrhedral coordination with respect to Z atoms. It results in localized moment of Mn atom and the magnetic moment is kind of robust against the Z atom.…”