Lecture-Intergranular Diffusion in Exchange-Coupled Sm-Co/Fe Nanocomposites and Thin Films

Speaker: Matthew J. Kramer

Time: 2011-06-10 　9:00 am　　 　　　　　　　　　　　　　　　　　　 

Place: Ningbo Institute of Material Technology and Engineering Chinese Academy of Sciences

Abstract

The nanostructural features, especially grain sizes, soft phase distribution and their grain boundaries are critical features which must be controlled to achieve exchange coupling necessary for enhanced hard magnetic properties. Using advanced microscopy techniques, we have investigated the Co-Fe interchange in SmCo5+Fe and Sm2Co7+Fe nanocomposites and thin films. We find that the behavior of the interdiffusion between the bcc soft phase and the magnetically hard phases are similar in thin films and bulk samples under similar annealing conditions: Co and Fe interdiffuse forming a Co40Fe60 bcc soft phase while the balance of the Fe forms a ternary Sm-Co-Fe phase of the initial phase. If the initial bcc phase has optimal Co content, substantial interdiffusion of Fe into the Sm-Co phases is not observed nor was the initial phase distributions retained. The magnetic properties of these alloys are inferior suggesting that optimal grain boundary chemistry is dependent on the appropriate local chemical driving forces.

Biography

A. Appointments

2002-present　  Senior Scientist, Division of Materials Science and Engineering (DMSE)

2001-present　　　  Group Leader, Materials Characterization/DMSE

1996-2001　　　　　  Scientist: Metallurgy and Ceramics Division, Ames Laboratory

1989-1995　　　　　  Associate Scientist: Metallurgy and Ceramics Division, Ames Laboratory

B. Academic Experience

2010-present　　　  Adjunct Professor: Department of Materials Science and Engineering

1996-2010　　　　　  Adjunct Associate Professor: Department of Materials Science and Engineering and Department of Geological and Atmospheric Sciences

1989-1995　　　　　  Assistant Adjunct Professor: Department of Geological and Atmospheric Sciences

C. Professional Societies

Materials Research Society, The Minerals, Metals and Materials Society and Microscopy Society of America

D. Areas of specialization

Structure and properties of glass forming metallic alloys, aperiodic intermetallic alloys, permanent magnets and high temperature alloys; development of in situ time resolved methods using electron microscopy and high energy X-ray diffraction; analytical electron microscopy; advanced imaging techniques for understanding rapid solidification

E. Technical Publications and Talks

Refereed Journal Publications: 251　　　　　　 Invited Talks: 52　　　　　　　　　　 Patents: 6