Magnetic, Caloric and Crystallographic Properties of Dy5(SixGe1-x)4 Alloys
- Iowa State Univ., Ames, IA (United States)
Polycrystals of the intermetallic compound of the Dy5(SixGe1-x)4 system, where x = 0, 0.25, 0.5, 0.625, 0.675, 0.725, 0.75, 0.775, 0.825, 0.875, and 1, have been prepared by electric-arc-melting on water-cooled copper hearth in an argon atmosphere. A study of phase relationships and crystallography in the pseudobinary system Dy5(SixGe1-x)4 using X-ray powder diffraction data and optical metallography was completed. It revealed that silicides in the composition range from 0.825 to 1 crystallize in the Gd5Si4-type crystal structure: germanides in the composition range from 0 to 0.625 crystallize in the Sm5Ge4-type structure, and alloys with intermediate composition range from 0.675 to 0.775 crystallize in the monoclinic Gd5Si2Ge2-type structure. The -ΔSm values were determined from magnetization measurements for 7 alloys. The alloys with a monoclinic crystal structure which belong to an intermediate phase region have large MCE value, which exceeds those observed in the other two phase regions by 300 to 500%. The nature of the observed magnetic and structural transformations in the Dy5(SixGe1-x)4 system seems to be similar with those reported for the Gd5(SixGe1-x)4 system. However, the interval and concentration range of three different phase regions in the Dy5(SixGe1-x)4 system are different from that observed in Gd-based alloys. A non-collinear ordering of magnetic moments at low temperature was observed for the alloys with monoclinic crystal structure. The Dy5Si3Ge alloy exhibited FM phase transition below Curie temperature. A series of magnetic transitions were observed at low temperature in the Dy5(SixGe1-x)4 alloys. The number of transitions increased and the magnetization decreased with increasing germanium content in the alloys. The -ΔSm and -ΔT values were calculated from heat capacity data for Dy5Si3.5Ge0.5 and Dy5Si4 alloys only, due to the fragile nature of the germanides-rich samples. Based on the MCe values, the alloys from the orthorhombic Dy5Si4-based solid solution and the intermediate monoclinic phase regions may be useful magnetic refrigerant materials in the temperature range ~50K to -160K.
- Research Organization:
- Ames Lab., Ames, IA (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC)
- DOE Contract Number:
- W-7405-Eng-82
- OSTI ID:
- 804161
- Report Number(s):
- IS-T 2075; TRN: US200302%%575
- Resource Relation:
- Other Information: TH: Thesis (M.S.); Submitted to Iowa State Univ., Ames, IA (US); PBD: 19 Jul 2002
- Country of Publication:
- United States
- Language:
- English
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