The magnetic structure in K+ beta-ferrite

The magnetic structures of stoichiometric, KFe11O17, and non-stoichiometric , K1.33Fe11O17, K+ beta-ferrite, have been studied with neutron powder diff raction at 10, 295 and 923 K. Parameters describing the crystal and magneti c structures were refined with the Rietveld method in the space group P6(3) /mmc. In both cases the magnetic structure is antiferromagnetic below 713 K with four different magnetic Fe atoms. In the non-stoichiometric compound a larger disorder in the magnetic structure is seen at 295 K than for the s toichiometric. This disorder could be attributed to the Fel atoms in 18h-si tes (x, 2x, z) and be seen as a function of the charge compensation of the excess of K+ ions in the non-stoichiometric sample. (C) 2000 Elsevier Scien ce B.V. All rights reserved.