Evolution of spatial spin-modulated structure with La doping in Bi1-yLayFeO3 multiferroics

Abstract In this paper we present study of the magnetic structure of multiferroic series Bi1-yLayFeO3 (y = 0, 0.015, 0.03, 0.05 and 0.10) using nuclear magnetic resonance (NMR) at 4.2 K and Mossbauer spectroscopy at room temperature on 57Fe nuclei. We observed the presence of cycloid type spatial spin-modulated structure (SSMS) in the whole range of compositions. The study of the concentration dependence of the anharmonicity parameter m revealed that at the temperature of liquid helium in the composition region y = 0 – 0.10 as well as at room temperature for y = 0.03 the magnetic state of multiferroics is described by cycloid type SSMS with a positive effective uniaxial constant of magnetic anisotropy Κu > 0 (“easy axis” model). The study at room temperature in turn revealed that magnetic state of the multiferroics with y = 0 – 0.03 is described by cycloid type SSMS with a positive effective uniaxial constant of magnetic anisotropy Κu > 0 (“easy axis” model). In contrast, the magnetic state of multiferroics with y = 0.05 and 0.10 is described by a negative effective uniaxial constant of magnetic anisotropy Κu