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RESEARCH PRODUCT
Probing the electronic states of high-TMR off-stoichiometric Co2MnSi thin films by hard x-ray photoelectron spectroscopy
Gerhard H. FecherClaudia FelserJulie KarelXeniya KozinaStanislav ChadovTakayuki IshikawaBenjamin BalkeMasafumi YamamotoKeisuke KobayashiSiham OuardiShigenori UedaEiji IkenagaTetsuya UemuraGregory Stryganyuksubject
Tunnel magnetoresistanceMaterials scienceX-ray photoelectron spectroscopyCondensed matter physicsFerromagnetismAb initio quantum chemistry methodsBand gapContent (measure theory)HeterojunctionThin filmCondensed Matter PhysicsElectronic Optical and Magnetic Materialsdescription
The tunnel magnetoresistance ratio (TMR) of fully epitaxial magnetic tunnel junctions with an off-stoichiometric Co${}_{2}$MnSi Heusler alloy has been shown to exhibit a systematic dependence on Mn content, reaching 1135% at 4.2 K for Co${}_{2}$Mn${}_{1.29}$Si. In this paper, we explain the behavior of the observed TMR ratio using ab initio calculations and hard x-ray photoelectron spectroscopy (HAXPES). For the Mn-deficient samples, we show that the the drop of the TMR is caused by Co antisite atoms, which impose extra states into the minority-spin band gap. On the other hand, Mn-excess composition shows nearly half-metallic behavior. This result can be intuitively understood since both Co${}_{2}$MnSi and Mn${}_{2}$CoSi are theoretically predicted to be half-metallic ferromagnets.
| year | journal | country | edition | language |
|---|---|---|---|---|
| 2014-03-17 | Physical Review B |