Atomic vibrational density of states in crystalline and amorphous Tb1−xFex alloy thin films studied by nuclear resonant inelastic x-ray scattering (NRIXS)

• Published in: Journal of physics. Condensed matter Vol. 16; no. 5; pp. S379 - S393
• Main Authors: Keune, W, Ruckert, T, Sahoo, B, Sturhahn, W, Toellner, T S, Alp, E E, Röhlsberger, R
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Bristol IOP Publishing 11.02.2004; Institute of Physics
• Subjects: Applied sciences; Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; Lattice dynamics; Metals. Metallurgy; Phonons in low-dimensional structures and small particles; Physics; Vibrational states in disordered systems; Moessbauer effect; Epitaxial layers; Force constants; Amorphous alloy; Phonon density of states; Iron alloys; Experimental study; Thin films; Thickness; Terbium alloys; Binary alloys; X-ray scattering; Inelastic scattering; Vibrational modes; Anharmonicity; Chemical composition; Synchrotron radiation
• ISSN: 0953-8984; 1361-648X
• DOI: 10.1088/0953-8984/16/5/004

Nuclear resonant inelastic x-ray scattering of 14.4125 keV synchrotron radiation was employed to measure directly the partial (Fe projected) vibrational density of states (VDOS), g(E), of vapour-quenched amorphous (a-)Tb1-x ,57Fex,- thin film alloys (0.20 # < x # < 0.82) and epitaxial Tb57Fe2(1 1 0) thin films. A comparison of the VDOS measured at 300 and 10 K, respectively, demonstrates that the vibrational anharmonicity is small in these systems. The probability of recoilless absorption (,f factor), the average kinetic energy per Fe atom and the average force constant were obtained. A plot of g(E)/E2 versus E proves the existence of non-Debye-like vibrational excitations at excitation energies below about 10 meV for the amorphous alloys. At a constant film thickness of 17.5 nm, the probability of these excitations scales about linearly with the Tb concentration.