Abstract: Particle morphology can result in very pronounced effects of crystallinity on the Mössbauer spectra of lepidocrocite. Such effects can noticeably increase the quadrupole splitting of poorly crystallized paramagnetic lepidocrocites, making it necessary to fit two doublets of different quadrupole splittings to Mössbauer spectra of such samples, and may lower the onset of magnetic ordering from the bulk Néel temperature of 77 ±1 K to about 50 K.

At 4.2 K, distributions of magnetic hyperfine fields with a limiting upper field of 460 kOe are observed. The contributions of lower fields to such distributions increase with decreasing crystallinity, producing asymmetrically broadened resonant lines.