Magnetostrictive and elastic properties of Fe 100 − x Mo x ( 2 < x < 12 ) single crystals

In this paper we investigate the magnetostrictive [ ( 3 / 2 ) λ 100 and ( 3 / 2 ) λ 111 ] and elastic ( c ′ and c 44 ) behavior of single crystalline alloys Fe 100 − x Mo x for 2 < x < 12 ; the magnetoelastic coupling constants ( − b 1 and − b 2 ) are computed from the measurements. Similar to other Fe-X ( X = Al , Ga, and Ge) alloys, the tetragonal magnetostriction ( 3 / 2 ) λ 100 increases monotonically from ∼ 70 × 10 − 6 at ∼ 2.5 at . % Mo to a maximum of either ∼ 100 × 10 − 6 at ∼ 8 at . % Mo for the slow cooled crystals or ∼ 125 × 10 − 6 at ∼ 11 at . % Mo for quenched crystals. A sharp decrease after the peak is observed for the slow cooled crystals due to the formation of a second phase. The rhombohedral magnetostriction ( 3 / 2 ) λ 111 of the Fe-Mo alloys is found to be insensitive to the Mo content. This behavior is distinctly different from other Fe-X ( X = Al , Ga, and Ge) alloys where a slight decrease in magnitude and a sign reversal upon chemical ordering was observed for ( 3 / 2 ) λ 111 . Both shear elastic constants ( c ′ and c 44 ) for Fe-Mo are remarkably insensitive to the Mo content, which is also distinct from the other Fe-based alloys used in the comparison. The two magnetoelastic coupling constants − b 1 = 3 λ 100 c ′ (with values from 7.15 to 9.77 MJ / m 3 ) and − b 2 = 3 λ 111 c 44 (with values from −4.96 to − 5.81 MJ / m 3 ) were calculated and compared with those of other Fe-X ( X = Al , Ga, and Ge) alloys.