Measurement of Young's modulus of nanocrystalline ferrites with spinel structures by atomic force acoustic microscopy

Abstract Using Atomic Force Acoustic Microscopy, the Young's moduli of two thin films of nanocrystalline ferrites with spinel structures have been measured as a function of the oxidation temperature on a nanoscale. There is an overall decrease of the Young's moduli as a function of the oxidation temperature with an intermediate minimum and maximum. These measurements corroborate the existence of chemical gradients from the surface layer to the interior of the films occurring during the oxidation process in the γ-phase. They lead to stress gradients which influence the Young's modulus and the coercivity Hc. In our measurement technique, we measure the flexural resonance frequencies of an atomic force microscope cantilever and exploit their dependence on the tip-sample contact forces, here an elastic contact described by Hertzian contact theory. The technique has been extended allowing quantitative measurements using a self-consistent calibration. Comparison to nanoindentation measurements have been made. We discuss possible nonlinear effects occurring in the contact which may lend AFAM itself to measure nonlinear parameters on a nanoscale.