Temperature dependence of magnetoelastic properties of Fe100-xSix (5 < x < 20)

Tetragonal magnetostriction (lambda(gamma,2)) and elastic constants (c', c(44), and c(11)) for Fe100-xSix were measured as a function of temperature (T). Compositions corresponding to the disordered A2 (x = 5), ordered D0(3) (x = 19.8), and mixed (x = 11.6) phases, were investigated. The magnetoelastic coupling (-b(1)) was determined for 77 < T < 300 K and compared with those of Fe-Ga, Fe-Ge, and Fe-Al. Both lambda(gamma,2) (T) and -b(1)(T) of Fe-Si behave similarly to those of Fe-Ge, while other notable differences exist between the measured properties of Fe-Si and those of the other three alloys. Due to the early establishment of short range order, Fe-Si exhibits a positive, although small, slope in lambda(gamma,2) (T) at 5 at. % Si, and a remarkable drop in -b(1) before the solubility limit. The weaker softening of the tetragonal shear modulus with the addition of Si and the lack of strong anharmonic effects in the Fe-Si lattice inferred from the weak T-dependence of all the moduli suggest that Fe-Si exhibits more structural stability than the other three alloys. The distinctive behavior is likely due to the smaller size of Si compared to the sizes of Ga, Ge and Al, and therefore to the effect of the larger size difference between Fe and Si in the Fe-Si lattice. (C) 2012 American Institute of Physics. [doi:10.1063/1.3673857]