Exceptional Combination of Large Magnetostriction, Low Hysteresis and Wide Working Temperature Range in (1-x)TbFe2-xDyCo2 Alloys

Magnetostrictive materials with large magnetostriction, low hysteresis and wide working temperature range are desired for applications, but rarely obtained so far. In this work, we report a surprising finding in (1-x)TbFe2-xDyCo2 alloys: the composition of x=0.5 exhibits a low hysteretic magnetostriction, λ//, max ~2066 ppm, which is 159% larger than that of the commercial giant magnetostrictive alloy of Terfenol-D, λ//, max ~1298 ppm. Moreover, its temperature range for λ// >1298 ppm is even larger than 240 K, and another working temperature window for λ// >1000 ppm is from 40 K to 324 K, which can cover a large temperature fluctuation in space environments (e.g. 120-290 K in Mars). The established phase diagram of (1-x)TbFe2-xDyCo2 by systematic studies of magnetic susceptibility, X-ray diffraction and convergent-beam electron diffraction results, shows an emergence of morphotropic phase boundary (MPB) between rhombohedral (R) and orthorhombic (O) ferromagnetic phases, which is different from the MPB between R and T (tetragonal) phases in (1-x)TbFe2-xDyFe2 . We reveal that the exceptional combination of giant magnetostriction, low hysteresis and wide working temperature range is caused by this R-O MPB. The comparison between R-O MPB and R-T MPB further shows the O phase plays a vital role in the property enhancement of R-O MPB composition. Our work indicates the construction of R-O MPB may provide a new way to find high-performance magnetostrictive materials.