Phonon Density of States of FeNi-Invar Determined by Nuclear Inelastic Scattering
Since more than 100 years the Invar effect is known. It is established, that the anomalous low expansion coefficient is strongly correlated to the magnetic properties (keyword: moment volume effect). The weakening of lattice vibrations is supposed to be responsible for the high spin — low spin transition. Due to the capabilities of nuclear inelastic scattering at 3rd generation synchrotron radiation sources it is possible to determine the local phonon density of states of iron. We have investigated a Fe65Ni35 Invar foil enriched in 57Fe in a range between 293 K and 540 K. Beside the local density of states the analysis delivers local thermodynamic properties such as Lamb-Mössbauer-factor and mean force constants which show anomalies near the Curie temperature.
KeywordsInvar nuclear inelastic scattering
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