Modulated magnetic structure of Fe3PO7 as seen by Fe57 Mössbauer spectroscopyстатья
Статья опубликована в высокорейтинговом журнале
Информация о цитировании статьи получена из
Web of Science,
Scopus
Статья опубликована в журнале из списка Web of Science и/или Scopus
Дата последнего поиска статьи во внешних источниках: 10 августа 2018 г.
Аннотация:The paper reports results of the 57Fe Mössbauer measurements on an Fe3PO4O3 powder sample recorded at
various temperatures, including the point of magnetic phase transition TN ≈ 163 K. The spectra measured above TN consist of a quadrupole doublet with high quadrupole splitting of 300 K ≈ 1.10 mm/s, emphasizing that Fe3+ ions are located in crystal positions with a strong electric-field gradient (EFG). To predict the sign and orientation of the main components of the EFG tensor, we calculated the EFG using the density-functional-theory approach. In the temperature range T <TN, the experimental spectra were fitted assuming that the electric hyperfine interactions are modulated when the Fe3+ spin (S) rotates with respect to the EFG axis, and with the emergence of spatial anisotropy of the hyperfine field Hhf ∝ A·S at 57Fe nuclei. These data were analyzed to estimate the components of the anisotropic hyperfine coupling tensor (A). The large anharmonicity parameter, m ≈ 0.94, of the spiral spin structure results from easy-axis anisotropy in the plane of the iron spin rotation. The temperature evolution of the hyperfine field Hhf(T) was described by the Bean-Rodbell model, which takes into account that the exchange magnetic interactions are a strong function of the lattice spacing. The obtained Mössbauer data are in qualitative agreement with previous neutron-diffraction data for a modulated helical magnetic structure in strongly frustrated Fe3PO4O3.