Magnetic and Structural Characterization of Fe-Ga Using Kerr Microscopy and Neutron Scattering
Abstract
Fe-Ga alloys belong to a class of smart materials called magnetostrictive materials. Magnetostrictive materials show dimensional (magnetostriction) and magnetization changes in response to magnetic and elastic fields. These effects can be utilized for transduction purposes. Most widely used magnetostrictive materials like Tb-Dy-Fe (Terfenol-D) show giant magnetostriction but suffer from low modulus of elasticity, low tensile strength and are extremely brittle, limiting their usage to applications involving only axial loads. Fe-Ga alloys have recently been discovered to show an extraordinary enhancement in magnetostriction with the addition of the nonmagnetic element, Ga. Though their magnetostriction is less than that of Terfenol-D, they boast superior properties such as ductile-like behavior, high tensile strengths (~ 400 MPa), low hysteresis, and low saturation fields (~ 10 mT). In this work, Fe-Ga alloys of various compositions and heat treatments were probed at different length scales - lattice level, nano-, micro-, and macro-scales. Neutron diffraction was used to probe the alloy at the lattice level to identify the existence of different phases. Small-Angle Neutron Scattering (SANS) experiments were used to study the nanoscale heterogeneities and their response to the applied magnetic and elastic fields. Ultra small-angle neutron scattering (USANS), magnetic force and Kerr microscopy were used to investigate the response of magnetic domains under externally applied magnetic and elastic fields. Piecing the results from lattice level, nano-, micro-, and macro-scales together with the macroscopic magnetostriction measurements, the nature of the magnetostriction in Fe-Ga alloys was uncovered. No evidence could be found that directly relates the presence of heterogeneities to the enhanced magnetostriction. Further, it was found that the observed heterogeneities were possibly of DO3 phase and are detrimental to the magnetostriction.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 2010
- Accession Number
- ADA596917
Entities
People
- Chaitanya Mudivarthi
Organizations
- University of Maryland