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

Using Atomic Force Acoustic Microscopy, the Young's moduli of two thin film s 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 th e existence of chemical gradients From the surface layer to the interior of the films occurring during the oxidation process in the gamma-phase. They lead to stress gradients which influence the Young's modulus and the coerci vity H-c. In our measurement technique, we measure the flexural resonance f requencies of an atomic force microscope cantilever and exploit their depen dence on the rip-sample contact forces, here an elastic contact described b y Hertzian contact theory. The technique has been extended allowing quantit ative measurements using a self-consistent calibration. Comparison to nanoi ndentation measurements have been made. We discuss possible nonlinear effec ts occurring in the contact which may lend AFAM itself to measure nonlinear parameters on a nanoscale. (C) 2000 Elsevier Science Ltd. All rights reser ved.