Combinatorial search of Fe-Ni-Cr system magnetostrictive alloys for force sensors

Abstract

Magnetostrictive materials of the Fe-Ni-Cr ternary system for sensitivity enhancement of force sensors were searched by using a combinatorial method. Magnetostrictive materials for force sensors require large magnetostriction, high relative permeability, and high resistivity. This research is an attempt to find composition ranges that satisfy the following requirements: magnetostriction greater than 20×10 -6, relative permeability greater than 4,000, and resistivity over 90 μΩ cm. A novel combinatorial deposition method, known as Combinatorial New Facing Targets Sputtering (Combi-NFTS) method was applied to fabricate libraries of samples with various compositions. Samples for measurement of the relative permeability and resistivity were synthesized with a composition distribution by using Combi-NFTS onto a 108 mm×76 mm glass substrate. After deposition of thin film, each sample is divided into 10 mm×10 mm. The relative permeability and resistivity were measured by using a vibrating sample magnetometer and the four probe method, respectively. Bilayer cantilever samples for evaluation of magnetostriction were fabricated onto a 6 mm×20 mm×0.1 mm Si substrate, whereby deflection of the samples changes when a magnetic field is applied. The laser lever method was used to measure the cantilever deflection. The results indicate that the composition range with an Fe content of 26-36.5 at.%, a Ni content of 61-66 at.%, and a Cr content of 7.5-9.5 at.% satisfy the requirement criteria.

Keywords

• combinatorial method
• magnetostriction
• sensor
• magnetostrictive material
• permeability
• resistivity
• combinatorial sputtering