Elastic modulus measurement of thin films coated onto magnetoelastic ribbons

A model is presented to describe the change of the resonant frequency of a magnetoelastic sensor when the sensor is coated with a material of given elasticity. With a mass load coated on the surface of the sensor, its characteristic resonant frequency changes depending on the ratio of the sound velocities in the sensor and the coating. A measurement technique is derived that allows the determination of Young´s modulus of elasticity of thin film coatings, with thickness greater than approximately 75 nm, based on the measurement of mass and resonant frequency of a sensor before and after coating. Comparing the measurement to the model delivers the value of Young´s modulus of elasticity for a coating of known density