English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Tools annual

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Presents the access of premium content as premium feature

Premium Content

Global: Zendy Plus annual

Global: Zendy Free Plan

Ni$_{80}$Fe$_{20}$ (Py) and Py-Cu exhibit intriguing ultrafastdemagnetization behavior, where the Ni magnetic moment shows a delayed responserelative to the Fe [S. Mathias et al., PNAS {\bf 109}, 4792 (2012)]. To unravelthe mechanism responsible for this behavior, we have studied Py-Cu alloys for awide range of Cu concentrations using X-ray magnetic circular dichroism (XMCD).The magnetic moments of Fe and Ni are found to respond very differently to Cualloying: Fe becomes a strong ferromagnet in Py, with the magnetic momentlargely unaffected by Cu alloying. In contrast, the Ni magnetic momentdecreases continuously with increasing Cu concentration. Our results arecorroborated by ab-initio calculations of the electronic structure, which wediscuss in the framework of virtual bound states (VBSs). For high Cuconcentrations, Ni exhibits VBSs below the Fermi level, which are likelyresponsible for an increased orbital/spin magnetic ratio at high Cuconcentrations. Fe exhibits VBSs in the minority band, approximately 1 eV abovethe Fermi level in pure Py, that move closer to the Fermi level upon Cualloying. A strong interaction between the VBSs and excited electrons above theFermi level enhances the formation of localized magnons at Fe sites, whichexplains the different behavior between Fe and Ni during ultrafastdemagnetization.

Localization of Fe d-states in Ni-Fe-Cu alloys and implications for ultrafast demagnetization