Title of Thesis: Magnetostriction and Magnetic Anisotropy of Fe 35 Co 65

Title of Thesis: MAGNETOSTRICTION AND MAGNETIC ANISOTROPY OF FE35CO65 Tong Ren, Master of Science, 2011 Thesis directed by: Professor Manfred Wuttig Materials Science and Engineering Department A Fe35Co65 single crystal has been prepared by a long time anneal at temperature close to its fcc-bcc phase boundary. Its magnetostriction constant λ100 and magnetocrystalline anisotropy constant K1 was measured using a strain gauge rosette and magnetization and torque magnetometer curves. The magnetostriction constant λ100 is as high as 200 ppm. The value of the anisotropy constant K1 and the value of the susceptibility were small and influenced by the magnetoelastic energy. The symmetry of the torque curves changes from 2-fold to 4-fold with increasing external field which indicates the existence of a second uniaxial phase. This result can be interpreted by the alignment of the magnetization of an epitaxial fcc precipitate in the bcc host by external field. MAGNETOSTRICTION AND MAGNETIC ANISOTROPY OF FE35CO65 by Tong Ren Thesis submitted to the Faculty of the Graduate School of the University of Maryland, College Park in partial fulfillment of the requirements for the degree of Master of Science 2011 Advisory Committee: Professor Manfred Wuttig, Chair Professor Alison Flatau Professor Abdellah Lisfi Professor James R. Cullen © Copyright by Tong Ren 2011