MÖSSBAUER EFFECT AND MAGNETIC PROPERTIES OF AN AMORPHOUS Fe2O3

Abstract
An amorphous iron (III) oxide was prepared by thermal decomposition of an aerosol on a heated substrate. Magnetic susceptibility measurements show a Néel temperature of 80 K. Below 50 K a thermoremanent moment is observed. The paramagnetic moment amounts to 2.5 µB per iron ion, indicating antiferromagnetic clustering. Mössbauer spectra show a paramagnetic doublet above 80 K with an isomer shift of + 0.15 mm/s and a quadrupole splitting of 1.01 mm/s ; below 80 K a hyperfine split spectrum is found with, at 5 K, Hhf = 470 kOe and ΔEQ = 0.11 mm/s. It is derived that the Fe3+ ions are coordinated by a distorted octahedron of O2- ions. Their symmetry axes are randomly oriented in the aperiodic lattice, leaving a wide distribution of angles ν between Hhf and Vz