Magnetocaloric effect of Gd₄(Bi_xSb_1-x)₃ alloy series

Thesis/Dissertation · Thu Dec 31 23:00:00 EST 1998

DOI:https://doi.org/10.2172/754836· OSTI ID:754836

Niu, Xuejun ^[1]

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1. Iowa State Univ., Ames, IA (United States)

Alloys from the Gd₄(Bi_xSb_1-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 I$$\bar{4}$$3d) 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.

• Research Organization: Ames Lab., Ames, IA (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: W-7405-ENG-82
• OSTI ID: 754836
• Report Number(s): IS-T--1894
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ANTIMONY ALLOYS
BISMUTH ALLOYS
CRYSTAL STRUCTURE
GADOLINIUM ALLOYS
MAGNETIC PROPERTIES
SPECIFIC HEAT