Magnetocaloric effect of Gd4(Bi[subscript x]Sb[subscript 1-x])3 alloy series
Date
1999
Authors
Niu, Xuejun
Major Professor
Advisor
Gschneidner, Karl A.
Pecharsky, Vitalij
Committee Member
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Alloys from the Gd4(Bi[Subscript x]Sb[Subscript l-x])3 series were prepared by melting a stoichiometric amounts of pure metals in an induction furnace. The crystal structure is of the anti-Th3P4 type (space group I4̄3d ) for all the compounds tested. The linear increase of the lattice parameters with Bi concentration is attributed to the larger atomic radius of Bi than that of Sb. Magnetic measurements show that the alloys order ferromagnetically from 266K to 330K, with the ordering temperature increasing with decreasing Bi concentration. The alloys are soft ferromagnets below their Curie temperatures, and follow the Curie-Weiss law above their ordering temperatures. The paramagnetic effective magnetic moments are low compared to the theoretical value for a free Gd3+, while the ordered magnetic moments are close to the theoretical value for Gd. The alloys exhibit a moderate magnetocaloric effect (MCE) whose maxima are located between 270K and 338K and have relatively wide peaks. The peak MCE temperature decreases with decreasing Bi concentration while the peak height increases with decreasing Bi concentration. The Curie temperatures determined from inflection points of heat capacity are in good agreement with those obtained from the magnetocaloric effect. The MCE results obtained from the two different methods (magnetization and heat capacity) agree quite well with each other for all of the alloys in the series.
Series Number
Journal Issue
Is Version Of
Versions
Series
Academic or Administrative Unit
Type
thesis