Structure–Composition-Magnetostriction Correlations in Strong Structure–Composition-Magnetostriction Correlations in Strong

and Ductile Fe-Based Alloys with Large Low-Field Magnetostrictionand Ductile Fe-Based Alloys with Large Low-Field Magnetostriction

Sivaraman Guruswamy, University of Utah, DMR 0854166

Research Focus

• Magnetostriction phenomenon refers to the change in the length of a material with applied magnetic field

• Magnetostrictive materials are used in numerous sensor, actuator and energy harvesting (Wind/Ocean) applications.

• Research examines how local atomic environment, crystalline structure and crystal defects influence the magnetostriction in -Fe based alloys.

Technical and Scientific ImpactThis is a significant contribution to a fundamental under-standing of magnetostriction. The work will help design alloys for sensor and actuators, energy harvesting, low-/zero-expansion structures, data storage media and other applications.

Significant Findings • Controlling inhomogeneous elastic strains introduced

by modifying local atomic spacing by solutes and defects, is key to controlling magnetostriction.

• Controlled introduction of dislocations by deformation involving only a single slip system dramatically decreases the magnetostriction. Deformation involving multiple slip system leads to a much smaller decrease.

Figure (top right) shows the Extended X-ray Absorption Fine Spectrum (EXAFS)* data (R) as a function of R and the fit from long-term annealed and quenched (LTA) Fe-15 at.% Ga single crystal. Data obtained at the Fe K edge. Data obtained on crystals with varying Ga contents and heat treatments. Near-neighbor distances measured indicate severe local lattice distortions.

Slip patterns BF TEM image

showing multiple slip.

BF TEM image showing single slip.

Education, Training and Outreach• Graduate students Gavin Garside, Biswadeep Saha, Chai Ren and M.

Ramanathan were trained in alloy synthesis, single crystal growth, XRD, magnetic measurements, SEM, TEM and EXAFS analysis.

• Chai Ren (2011) and Gavin Garside (2009) attended the Neutron and X-ray Scattering School at ORNL / ANL.

• PhD students Gavin, Biswadeep, Chai and M. Ramanathan graduated with and are gainfully employed. Gavin is with ATI-Wah Chang. M. Ramanathan and Biswadeep were hired by INTEL on graduation this summer. Dr. Chai Ren was hired as a Post-Doctoral fellow by Prof. Fang at the University of Utah up on his graduation this summer.

• Graduate students presented 5 papers at TMS 2011 & 4 papers at TMS 2012.

• Showcased the lab and research again to high school students, visitors and public during Science day, and Open House events held during 2012.

Structure-Composition-Magnetostriction Correlations in Strong Structure-Composition-Magnetostriction Correlations in Strong

and Ductile Fe-Based Alloys with Large Low-Field Magnetostrictionand Ductile Fe-Based Alloys with Large Low-Field MagnetostrictionSivaraman Guruswamy, University of Utah, DMR 0854166

Recognitions• PI was recognized as an ASM Fellow in July, 2011 for his outstanding

contributions to the development of Fe-Ga magnetostrictive alloys and cable sheathing alloys, and for his outstanding contribution to the education and mentoring of students

• PI recognized with 2010 Univ. of Utah Distinguished Teaching Award and 2010 Associated Students of Univ. of Utah (ASUU) Student Choice Award

• PI mentored the student team that won the Materials Bowl held during TMS 2011 in San Diego. Two students from this research group (Biswadeep and M. Ramanathan) were members of the team.

Graduate students Gavin, Chai and Biswadeep being trained in the use of a Vibrating Sample Magnetometer System

Graduate students Biswadeep and M.Ramanathan preparing the alloy by arc-melting prior to single crystal growth.