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The Role of Disorder in the Magnetic Properties of Mechanically Milled Nanostructured Alloys

Published online by Cambridge University Press:  21 March 2011

Diandra L. Leslie-Pelecky
Affiliation:
Center for Materials Research and Analysis and Department of Physics & Astronomy, University of Nebraska, Lincoln NE 68588-0111
Elaine M. Kirkpatrick
Affiliation:
Center for Materials Research and Analysis and Department of Physics & Astronomy, University of Nebraska, Lincoln NE 68588-0111
Tom Pekarek
Affiliation:
Department of Chemistry and Physics, University of North Florida, Jacksonville, FL 32224
Richard L. Schalek
Affiliation:
Composite Materials and Structures Center, Michigan State University, East Lansing MI, 48824
Paul Shand
Affiliation:
Physics Department, University of Northern Iowa, Cedar Falls, Iowa 50614
Deborah S. Williams
Affiliation:
Center for Materials Research and Analysis and Department of Physics & Astronomy, University of Nebraska, Lincoln NE 68588-0111
Lanping Yue
Affiliation:
Center for Materials Research and Analysis and Department of Physics & Astronomy, University of Nebraska, Lincoln NE 68588-0111
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Abstract

Mechanical milling provides a unique means of studying the influence of grain size and disorder on the magnetic properties of nanostructured alloys. This paper compares the role of milling in the nanostructure evolution of two ferromagnets – SmCo5 and GdAl2 – and the subsequent impact of nanostructure on magnetic properties and phase transitions. The ferromagnetic properties of SmCo5 are enhanced by short (< 2 hours) milling times, producing up to an eight-fold increase in coercivity and high remanence ratios. The coercivity increase is attributed to defect formation and strain. Additional milling increases the disorder and produces a mix of ferromagnetic and antiferromagnetic interactions that form a magnetically glassy phase. GdAl2, which changes from ferromagnetic in its crystalline form to spin-glass-like in its amorphous form, is a model system for studying the dependence of magnetically glassy behavior on grain size and disorder. Nanostructured GdAl2 with a mean grain size of 8 nm shows a combination of ferromagnetic and magnetically glassy behavior, in contrast to previous studies of nanostructured GdAl2 with a grain size of 20 nm that show only spin-glass-like behavior.

Type
Research Article
Copyright
Copyright © Materials Research Society 2001

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