Mossbauer study of antiferromagnetic CuFeO2

We have studied the magnetic spin structure of antiferromagnetic CuFeO2 by X-ray diffraction (XRD) and Mossbauer spectroscopy. Its crystal structure determined by XRD analysis was a rhombohedral structure ( space group R-3m) and lattice constants a(0) and c(0) were 3.0333 and 17.1595 angstrom, respectively. In spite of 4-Fe sublattices in a delafossite CuFeO2, its Mossbauer spectra were analyzed with 1-set (6-Lorentzian lines) below 10K due to the collinear-commensurate spin structure, but the spectra were fitted with 4-sextet above 10K due to the incommensurate spin structure. This phenomenon was attributed to the spin-lattice relaxation effect. Magnetic Neel temperature was also determined at 18 K, which corresponded to the high-spin Fe3+ valance state. On the other hand, CuFe0.98Al0.02O2 powder with a noncollinear spin structure was fitted with 4-sextet at 4.2 K. (c) 2008 Elsevier B.V. All rights reserved.