Incommensurate spin density wave in Co-doped BaFe2As2

Fe-57 Mossbauer spectroscopy measurements are presented in the underdoped Ba(Fe1-xCox)(2)As-2 series for x=0.014 (T-c < 1.4K) and x=0.03 and 0.045 (T-c similar or equal to 2 and 12K, respectively). The spectral shapes in the so-called spin density wave (SDW) phase are interpreted in terms of incommensurate modulation of the magnetic structure, and allow the shape of the modulation to be determined. In undoped BaFe(2)A(s)2, the magnetic structure is commensurate, and we. nd that incommensurability is present at the lowest doping level (x= 0.014). As Co doping increases, the low-temperature modulation progressively loses its squaredness and tends to a sine-wave. The same trend occurs for a given doping level, as temperature increases. We. nd that a magnetic hyper. ne component persists far above the SDW transition, its intensity being progressively tranferred to a paramagnetic component on heating. Copyright (C) EPLA, 2010 Resistivity