Atomic vibrational density of states in crystalline and amorphous Tb_1 xFe_xalloy thin films studied by nuclear resonant inelastic x-ray scattering (NRIXS)

Abstract

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-)Tb 1−x 57 Fe x thin film alloys (0.20 x 0.82) and epitaxial Tb 57 Fe 2 (110) 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)/E 2 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.

Amorphous Fe–Mg alloy thin films: magnetic properties and atomic vibrational dynamics

“…Apparently, the anomalous low-energy excitations in these amorphous Fe-alloys are related to vibrational modes induced by the non-ferrous atoms. Similar behavior was observed earlier for a-Fe x Tb 1−x alloy films [28].…”

“…The VDOS is a fundamental quantity from which important thermodynamic properties may be deduced [12][13][14][15][16][17][18][19][20]. Because only small quantities of materials are needed, NRIXS is suitable for the study of lattice dynamics in thin films, at interfaces and in multilayers [21][22][23][24][25][26][27][28][29][30][31].…”

“…After a comprehensive investigation of the amorphous (a-) Fe x Tb 1−x thin film system [28], here we report on the magnetic and vibrational properties of a-Fe x Mg 1−x alloy thin films. We expect that the difference in atomic mass, atomic radius and electron affinity modifies the amplitude (height) and energy of the boson peak.…”

Vibrational dynamics of Fe in amorphous Fe–Sc and Fe–Al alloy thin films

“…The existence of such excess vibrational excitations in different bulk materials [8] and in particular in metallic glasses [9] was revealed by earlier inelastic neutron scattering results. More recently, nuclear resonant inelastic X-ray scattering (NRIXS) of synchrotron radiation at 57 Fe nuclei has been used to measure the boson peak via ferrocene probe molecules matrixisolated in various bulk organic glasses [3], and in various amorphous binary alloy thin-film systems [10][11][12][13][14][15][16][17][18]. A systematic NRIXS investigation of vapor-quenched amorphous (a-) Fe x Tb 1−x [16] and a-Fe x Mg 1−x [18] alloy thin films was reported recently.…”

“…More recently, nuclear resonant inelastic X-ray scattering (NRIXS) of synchrotron radiation at 57 Fe nuclei has been used to measure the boson peak via ferrocene probe molecules matrixisolated in various bulk organic glasses [3], and in various amorphous binary alloy thin-film systems [10][11][12][13][14][15][16][17][18]. A systematic NRIXS investigation of vapor-quenched amorphous (a-) Fe x Tb 1−x [16] and a-Fe x Mg 1−x [18] alloy thin films was reported recently. These results demonstrate that the features of the boson peak in a-Fe x M 1−x alloys depends on the alloy composition and on the type of alloying element M. Therefore, in order to obtain information on the nature of the boson peak in metallic glasses it is essential to study systematically the vibrational properties of binary a-Fe x M 1−x alloys as a function of atomic mass, atomic volume and electronegativity of the element M. The present work is a continuation of our previous systematic studies of the properties of the boson peak in amorphous binary-alloy thin films.…”