Electric field gradients in amorphous metals

The⁵⁷Fe-Mössbauer spectroscopy has been used in order to study the quadrupole splitting E_Q at the Fe-site and its dependence on temperature in Fe_85–XCr_XB₁₅ and Fe_80–XMo_XB₂₀ amorphous alloys. In all investigated compositions the local symmetry was lower than cubic with room temperature values of E_Q in the range of 0.4–0.5 mm/s. In all cases relatively broad distributions of E_Q and therefore of the EFG have been obtained. The EFG of the investigated compounds changes reversibly with temperature up to about 650 K according to the relation E_Q (T)=E_Q (O)·(1-BTV^3/2) as in the case of crystalline noncubic metals. Assuming that the same dependence of B on the Debye temperature as in crystalline non-cubic metals holds for amorphous alloys, values of have been obtained in good agreement with those determined from the temperature dependence of the Mössbauer f-factor.