The Piezomagnetic Matteucci Effect in Nickel Alloys: Development of Theory and Applications

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This project lays the groundwork for a description of the Matteucci phenomenon. The research concentrates on one relatively simple class of materials known as permalloys in which magnetostriction can be controlled via the alloy composition. The project includes specimen preparation, structural characterization, and measurements of the changes in magnetic properties under torsional stress at different temperatures and magnetic field strengths. The work will develop a first principles, non-linear, hysteretic, theoretical model of the phenomenon. Nickel is the main material of choice for providing a reliable set of basic data; it has many advantages over other magnetic materials because of its relatively high magnetostriction, low anisotropy and high sensitivity to applied stress. In addition the magnetostriction coefficients along the 100 and 111 directions are comparable, resulting in a simpler dependence of magnetostriction on field. Nickel can be alloyed with iron to produce a series of materials with magnetostriction coefficients ranging from +7 ppm to -35 ppm, so that the dependence of the response on the magnetoelastic properties of the materials can be tested. All of these factors are an advantage in the search for a model to describe the observed behavior of the materials. This work will document the behavior of a relatively simple magnetic system under the action of torsional stress, will examine the magnetic response of these materials to torque under a variety of experimental conditions, and will develop model equations that help us to understand the performance of the material. %%%The Matteucci effect, that is the change of magnetization of a material with torsional stress, is currently of great technological interest because of the search for materials for magnetic torque sensors. Magnetic properties of materials, particularly magnetization, are very sensitive to stress, and yet this behavior is poorly understood from a scientific viewpoint. This is because the Matteucci effect is non-linear and path dependent (hysteretic). At present there is no adequate theory that can be used to accurately describe this behavior.***