Claims
- 1. Heat treated material comprising Gd5(SixGe1−x)4 where 0.47≦x≦0.56 exhibiting a magnetic entropy change (−ΔSm) of at least 16 J/kg K for a magnetic field change of 0 to 50 kOe at a temperature of about 300K and below.
- 2. The material of claim 1 also exhibiting a magnetostriction of at least 2000 parts per million and a magnetoresistance of at least 5%.
- 3. The material of claim 1 having a homogeneous microstructure comprising monoclinic crystallographic phase Gd5(SixGe1−x)4 for 0.47≦x≦0.56 and orthorhombic (II) crystallographic phase Gd5(SixGe1−x)4 for a mixture thereof for 0.5≦x≦0.56.
- 4. The material of claim 1 having been heat treated between 800 to 1600 degrees C. for a time.
- 5. Heat treated material comprising R5(SixGe1−x)4 where 0≦x≦1.0 and R is one or more rare earth elements other than Gd and exhibiting a magnetic entropy change (−ΔSm) of at least 10 J/kg K for a magnetic field change of 0 to 50 kOe at a temperature of about 300K and below.
- 6. The material of claim 5 also exhibiting a magnetostriction of at least 2000 parts per million and a magnetoresistance of at least 5%.
- 7. Heat treated material comprising (R1−yR′y)5(SixGe1−x)4 where 0≦y≦1.0and 0≦x≦1.0 and where R and R′ each is a rare earth element and at least one of R and R′ is other than Gd, and exhibiting a magnetic entropy change (−ΔSm) of at least 10 J/kg K for a magnetic field change of 0 to 50 kOe at a temperature of about 300K and below.
- 8. The material of claim 7 also exhibiting a magnetostriction of at least 2000 parts per million and a magnetoresistance of at least 5%.
- 9. In a method of making a material comprising Gd5(SixGe1−x)4 where 0.47≦x≦0.56, the improvement comprising heat treating an as-cast body comprising said material at a temperature between 800 to 1600 degrees C. for a time that said material after said heat treating exhibits a magnetic entropy change (−ΔSm) of at least 16 J/kg K for a magnetic field change of 0 to 50 kOe at a temperature of about 300K and below.
- 10. The material of claim 9 also exhibiting a magnetostriction of at least 2000 parts per million and a magnetoresistance of at least 5%.
- 11. The method of claim 9 wherein said material is made by melting amounts of Gd, Si, and Ge under subambient pressure to form a melt thereof and to oxidize and reduce an amount of carbon present in the Gd component and then solidifying said melt.
- 12. The method of claim 11 wherein said material after heat treating is cooled to ambient temperature sufficiently fast to avoid crystallographic transformation of a monoclinic phase to an orthorhombic phase for 0.47≦x≦0.56.
- 13. In a method of making a material comprising R5(SixGe1−x)4 where 0≦x≦1.0 and R is one or more rare earth elements other than Gd, the improvement comprising heat treating an as-cast body comprising said material at a temperature between 800 to 1600 degrees C. for a time that said material after said heat treating exhibits a magnetic entropy change (−ΔSm) of at least 10 J/kg K for a magnetic field change of 0 to 50 kOe at a temperature of about 300K and below.
- 14. The material of claim 13 also exhibiting a magnetostriction of at least 2000 parts per million and a magnetoresistance of at least 5%.
- 15. The method of claim 13 wherein said material is made by melting amounts of R, Si, and Ge under subambient pressure to form a melt thereof and to oxidize and reduce an amount of carbon present in the Gd component and then solidifying said melt.
- 16. The method of claim 13 wherein said material after heat treating is cooled to ambient temperature sufficiently fast to avoid crystallographic transformation of a monoclinic phase to an orthorhombic phase for 0≦x≦1.0.
- 17. In a method of making a material comprising (R1−yR′y)5(SixGe1−x)4 where 0≦y≦1.0 and 0≦x≦1.0 and R and R′ each is a rare earth element and at least one of R and R′ is other than Gd, the improvement comprising heat treating an as-cast body comprising said material at a temperature between 800 to 1600 degrees C. for a time that said material after said heat treating exhibits a magnetic entropy change (−ΔSm) of at least 10 J/kg K for a magnetic field change of 0 to 50 kOe at a temperature of about 300K and below.
- 18. The material of claim 17 also exhibiting a magnetostriction of at least 2000 parts per million and a magnetoresistance of at least 5%.
- 19. The method of claim 17 wherein said material is made by melting amounts of R, R′, Si, and Ge under subambient pressure to form a melt thereof and to oxidize and reduce an amount of carbon present in the Gd component and then solidifying said melt.
- 20. The method of claim 17 wherein said material after heat treating is cooled to ambient temperature sufficiently fast to avoid crystallographic transformation of a monoclinic phase to an orthorhombic phase for 0≦x≦1.0.
RELATED APPLICATION
[0001] The application is a continuation-in-part of Ser. No. 09/793,822 filed on Feb. 23, 2001, claiming benefit of provisional application Serial No. 60/187,713 filed Mar. 8, 2000.
CONTRACTUAL ORIGIN OF INVENTION
[0002] The United States Government has rights in this invention pursuant to Contract No. W-7405-ENG-82 between the U.S. Department of Energy and Iowa State University, Ames, Iowa, which contract grants to the Iowa State University Research Foundation, Inc. the right to apply for this patent.
Provisional Applications (1)
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Number |
Date |
Country |
|
60187713 |
Mar 2000 |
US |
Continuation in Parts (1)
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Number |
Date |
Country |
Parent |
09793822 |
Feb 2001 |
US |
Child |
10413417 |
Apr 2003 |
US |