ИСТИНА

Introduction One of the main tasks in the study of multiferroics based on bismuth orthoferrite is the search for the most suitable for industrial application dopant and the required degree of doping. The optimal composition is supposed to modify the spatial spin-modulated structure (SSMS) characteristic of the parent BiFeO3 compound and realize the potential of the magnetoelectric effect of the material [1, 2]. The samples and characterization In this work, samples of bismuth orthoferrite doped with Tb in the A position with x = {1.5%, 5%, 16%} obtained by solid-phase synthesis were studied. X-ray analysis showed that most of the samples possess the rhombohedral R3c structure. NMR spectroscopy data All samples were studied using 57Fe NMR spectroscopy in zero field at 4.2 K (Fig. 1). It was found that, in the substitution range of 1.5–5%, SSMS provides a different response strongly dependent on the amplitude of the applied RF pulses up to a change in the type of anisotropy. In general, small degrees (1.5; 3%) of doping result in the anharmonicity parameter m being reduced compared to parent bismuth ferrite. However, when studying a sample with a substitution of 8.5%, it was found that the the above effect almost disappears and “easy plane” type anisotropy with m almost equal to 1 is observed, which indicates the degeneration of the SSMS into almost a collinear structure. To the right of the main spectrum, at a frequency of 75.85 MHz, an additional low-intensity high-frequency line was detected. A similar phenomenon was previously observed when bismuth was replaced by La and Sr and can be associated with Fe atoms in the immediate vicinity of the corresponding ligands [3, 4].