Phonon density of states in epitaxial Fe/Cr(001) superlattices

Conference · Thu Oct 21 04:00:00 EDT 1999

OSTI ID:750539

Ruckert, T; Keune, W; Sturhahn, W; Hu, M Y; Sutter, J P; Toellner, T S; Alp, E E

Incoherent nuclear resonant absorption of synchrotron radiation at the 14.413 keV nuclear resonance of {sup 57}Fe was employed to measure directly the Fe-projected (partial) photon density of states (DOS) in epitaxial [Fe(8.7ML)/Cr(8ML)]{sub 200} superlattices and alloy films MBE-grown on MgO(001). Isotopically depleted {sup 56}Fe was used which gives no resonance signal. 0.7 monolayers (ML) thick {sup 57}Fe-probe layer (1{angstrom}) of 95.5% enrichment were placed either at the {sup 56}Fe-on-Cr interfaces or at the center of the {sup 56}Fe layers, thus providing a nuclear resonance signal from different places in the films. In addition, the authors prepared an epitaxial film which contains only a 1{angstrom}-thick {sup 57}Fe submonolayer in Cr(001) and no {sup 56}Fe layers. Moreover, they prepared a 7000 {angstrom}-thick epitaxial {sup 57}Fe{sub 0.03}Cr{sub 0.97}(001) alloy film. The measurements were performed at 300 K with 2.3 meV energy resolution around 14.413 keV. The phonon DOS of the center site was found to be very similar to that of bulk bcc Fe. Compared to the center site, the DOS of the other samples show distinct differences. In particular, longitudinal vibrations of Fe atoms are suppressed at the Fe/Cr interfaces.

• Research Organization: Argonne National Lab., IL (US)
• Sponsoring Organization: US Department of Energy (US)
• DOE Contract Number: W-31109-ENG-38
• OSTI ID: 750539
• Report Number(s): ANL/XFD/CP-100200
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
CHROMIUM
CHROMIUM BASE ALLOYS
IRON
IRON 57
IRON ALLOYS
LATTICE VIBRATIONS
LAYERS
MOESSBAUER EFFECT
PHONONS
SUPERLATTICES