#### Document Type

Conference Proceeding

#### Conference

55th Annual Conference on Magnetism and Magnetic Materials

#### Publication Date

3-18-2011

#### City

Atlanta, GA

#### Abstract

The contrast between the saturation tetragonal magnetostriction, λ^{γ,2} = (3/2)λ_{100}, of Fe_{1−x}Ga_{x} and Fe_{1−y}Ge_{y}, at compositions where both alloys exhibit D0_{3} cubic symmetry (*second peak* region), was investigated. This region corresponds to *x* = 28 at. % Ga and *y* = 18 at. % Ge or, in terms of *e*/*a* = 2 *x* + 3 *y* + 1, to an *e*/*a* value of ∼1.55 for each of the alloys. Single crystal, slow-cooled, ternary Fe_{1−x−y} Ga_{x}Ge_{y} alloys with *e*/*a* ∼1.55 and gradually increasing *y*/*x* were investigated experimentally (magnetostriction, elasticity, powder XRD) and theoretically (density functional calculations). It was found that a small amount of Ge (*y* = 1.3) replacing Ga in the Fe–Ga alloy has a profound effect on the measured λ^{γ,2}. As *y* increases, the drop in λ^{γ,2} is considerable, reaching negative values at *y*/*x* = 0.47. The two shear elastic constants *c*′ = (*c*_{11}− *c*_{12})/2 and *c*_{44} measured for four compositions with 0.06 ≤ *y*/*x* ≤ 0.45 at 7 K range from 16 to 21 GPa and from 133 to 138 GPa, respectively. Large temperature dependence was observed for *c*′ but not for *c*_{44}, a trend seen in other high-solute Fe alloys. The XRD analysis shows that the metastable D0_{3} structure, observed previously in slow-cooled Fe–Ga at *e*/*a* = 1.55, is replaced with two phases, fcc L1_{2} and hexagonal D0_{19}, at just 1.6 at. % Ge. The two are the *stable*phases of the assessed Fe–Ga phase diagram at *x* ∼ 28. Notably, at *y* = 7.8, only the D0_{3}phase (the equilibrium phase of Fe–Ge at *e*/*a* = 1.54) was found in the ternary alloy. The theory also shows that the D0_{3} instability is removed for compositions with *y* ≥ 3.9, when D0_{3} becomes the structure’s ground-state phase. Thus, the high, positive λ^{γ,2} value for Fe–Ga at *x* = 28 could be the result of the high sensitivity of its metastable D0_{3} structure.

#### Copyright Owner

American Institute of Physics

#### Copyright Date

2011

#### Language

en

#### Recommended Citation

Petculescu, G.; Ledet, K. L.; Huang, Mianliang; Lograsso, Thomas A.; Zhang, Y. N.; Wu, R. Q.; Wun-Fogle, M.; Restorff, J. B.; Clark, A. E.; and Hathaway, K. B., "Magnetostriction, elasticity, and D03 phase stability in Fe–Ga and Fe–Ga–Ge alloys" (2011). *Ames Laboratory Conference Papers, Posters, and Presentations*. 5.

http://lib.dr.iastate.edu/ameslab_conf/5

## Comments

Copyright 2011 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics.

The following article is from

Journal of Applied Physics109 (2011): 07A904 and may be found at http://dx.doi.org/10.1063/1.3535444.