ISSN:
1600-5724
Source:
Crystallography Journals Online : IUCR Backfile Archive 1948-2001
Topics:
Chemistry and Pharmacology
,
Geosciences
,
Physics
Notes:
The compound Bi2Fe4O9 belongs to the space group Pbam ( D92h), with two formula units per unit cell. Neutron diffraction measurements showed that it is paramagnetic at room temperature and undergoes a transition to an antiferromagnetic state at TN = (264 ± 3) K in agreement with previous susceptibility and Mössbauer measurements. Analysis of the 80 K neutron diffraction pattern yielded a magnetic structure with the following features: (a) The basic translations ao, bo, co of the chemical lattice change into antitranslations in the magnetic lattice. (b) The spins are perpendicular to co. (c) The magnetic structure belongs to the PC2/m space group and is a basis vector to an irreducible space under the Pbam irreducible representations, in accord with Landau's theory of second-order phase transition. The position parameters of the Fe3+ ions in the unit cell were refined. The magnetic moment of the compound was found to be (4.95 ± 0.08) μB, compared with the value of 5 μB for the Fe3+ free ion. The temperature dependence of the { 131 } magnetic reflection peak intensity was measured and found to be in agreement with the sublattice magnetization predicted by the molecular field approximation.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1107/S0567739478001412
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