Spiral magnetic structures with various helix parameters in langasite family compounds tested by Moessbauer spectroscopy

摘要

A physico-mathematical model for processing the Mossbauer spectra of the langasite family compounds with a helical magnetic structure was developed. It was shown that the Mossbauer spectra demonstrate high information content and sensitivity to details of the magnetic structure even in the case of polycrystalline samples and in the absence of an external magnetic field. In addition, they make it possible to monitor the dynamics of the magnetic structure in the entire temperature range below the Neel point. As an example, the helical magnetic structure in the langasite Ba_3SbFe_3Si_2O_(14) was experimentally investigated. It was established that during translation along the c axis, the magnetic moments of iron in the (ab) planes rotate at an angle of 72°, forming a spiral with a period of 5c. The directions of the main axis of the electric field gradient (EFG) and the local axis of magnetic anisotropy were determined, which are very important characteristics of the frustrated magnetic structure of langasites.