Mössbauer study of magnetism in FeII − III (oxy-)hydroxycarbonate green rusts; ferrimagnetism of FeII − III hydroxycarbonate
Résumé
FeII − III hydroxycarbonate FeII4FeIII2(OH)12CO3, green rust GR(CO2−3), reveals a ferrimagnetic behaviour. Moments that lie within two-dimensional cation layers are parallel for same species and antiparallel between FeII and FeIII. Respective ordering temperatures are 5.2 and 7 K. A sextet with distribution from 350 to 580 kOe for FeIII and an octet reflecting a mixture of states with field of 130 kOe and quadrupole splitting of −3.0 mm s − 1 for FeII are observed at 1.4 K. Ferric oxyhydroxycarbonate FeIII6O12H8CO3 is ferromagnetic and displays at 4 K a sextet with field between 400 and 500 kOe (maximum at 480 kOe) and transition at 80 K. GR(CO2−3) deprotonation gives magnetic domains with compositions at x = 1/3, 2/3 and 1 due to long range order.