Magnetic structure of sodium and potassium doped lanthanum manganites

Neutron diffraction, depolarization, and magnetization measurements were carried out on Na (La0.82Na0.13MnO2.93) and K (La0.82K0.08MnO2.89) doped lanthanum manganites. The study shows that both the compounds are ferromagnetic below 300 K. Low-temperature magnetic structure refinement together with the magnetization (M) measurements suggest that both the compounds have a canted ferromagnetic structure at 14 K. Smooth variation of the magnetic peak intensity (proportional to M-2) as a function of temperature could be fitted to the mean field approximation relationship, which indicates that, there is no abrupt change in the canting angle with temperature. Magnetic domain size (which is restricted by the grain size in the polycrystalline samples) obtained from the neutron depolarization measurements was found to be similar to 1-2 mu m in a magnetic field of 1.2 kOe for both samples. (C) 2000 Elsevier Science Ltd. All rights reserved.