Structural and magnetoelastic properties of non-stoichiometric TbFe2Mn Laves phase

In this paper, we studied TbFe 2 Mn x alloys using x-ray powder diffraction, x-ray fluorescent analysis, differential scanning calorimetry, scanning electron microscopy, and magnetostriction measurements. It was established that single phase non-stoichiometric TbFe 2 Mn x compounds are formed up to Mn concentration x = 0.25. The non-stoichiometric TbFe 2 Mn x compounds possess huge spontaneous magnetostriction in [111] direction (up to 2550 ppm) which result to distortion cubic MgCu 2 -type structure to rhombohedral ( R 3 ¯ m ) at room temperature. The formation of non-stoichiometric TbFe 2 Mn x compounds results from partial substitution of Tb by Mn in (6 c ) positions. It was found a characteristic value for the cubic MgCu 2 -type lattice parameter a c ≈ 7.2 Å. If binary RT 2 ( R is a rare-earth metal, T – 3 d transitional metal) compounds have lattice parameter smaller than 7.2 Å, we can expect large values of Mn concentration ( x > 0.4) in non-stoichiometric RT 2 Mn x compounds. The Mn doping in TbFe 2 Mn 0.25 compound led to significant increase of magnetostriction at liquid nitrogen temperature ( λ || ≈ 2400 ppm in magnetic field 18 kOe) which is 25 % larger than that of initial TbFe 2 . It also preserve large magnetostriction at room temperature ( λ || ≈ 1530 ppm in magnetic field 18 kOe). This make non-stoichiometric TbFe 2 Mn 0.25 compound promising material for various magnetostrictive applications in wide temperature range. • Significant increase of longitudinal magnetostriction for TbFe 2 Mn x was observed. • The parameter for maximum Mn concentration of RT 2 Mn x compounds was found. • Compounds show giant magnetostrictive distortions in unit cell. • Calculated and discussed Mn occupation of Tb sites in TbFe 2 Mn x compounds.