Magnetic transitions in disordered GdAl₂

Authors

D. S. Williams, University of Nebraska - Lincoln
Paul M. Shand, University of Northern IowaFollow
Thomas M. Pekarek, University of Northern FloridaFollow
Ralph Skomski, University of Nebraska-LincolnFollow
Valeri G. Petkov, Central Michigan UniversityFollow
Diandra Leslie-Pelecky, University of Nebraska - LincolnFollow

Date of this Version

12-3-2003

Comments

Published in Physical Review B, 68, 214404 (3 December 2003)
Copyright © 2003 The American Physical Society. Used by permission
URL: http://link.aps.org/abstract/PRB/v68/e214404
doi:10.1103/PhysRevB.68.214404

Abstract

The role of disorder in magnetic ordering transitions is investigated using mechanically milled GdAl₂. Crystalline GdAl₂ is a ferromagnet while amorphous GdAl₂ is a spin glass. Nanostructured GdAl₂ shows a paramagnetic-to-ferromagnetic transition and glassy behavior, with the temperature and magnitude of each transition dependent on the degree and type of disorder. Disorder is parametrized by a Gaussian distribution of Curie temperatures T_C with mean T_C and breadth Δ T_C. A nonzero coercivity is observed at temperatures more than 20 K above the highest T_C of any known Gd-Al phase; however, the coercivity decreases with decreasing temperature over the same temperature range where the GdAl₂ grains ferromagnetically order. Models for the anomalous coercivity behavior are proposed and evaluated for their ability to explain the origin of the low-temperature glassy magnetization peak.