ISSN:
1432-2021
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
,
Geosciences
,
Physics
Notes:
Abstract Magnetic properties of two samples of crocidolite (blue asbestos) have been examined using susceptibility and magnetization measurements, neutron diffraction, and Mössbauer spectroscopy. Both samples order magnetically at 30±1 K with a structure in which iron ions in the ribbons parallel to c are all coupled ferromagnetically but the moments of adjacent ribbons are oppositely aligned. The iron moments are oriented at angles of about 69°, 36°, 69° with the a, b, c axes, respectively. A spin flop transition of the antiferromagnetically coupled ribbons occurs in an applied field of 15 kOe at 4.2 K, and a ratio of intraribbon to interribbon exchange interactions of about 10 is inferred. Mössbauer spectra at 4.2 K are decomposed into a ferric pattern with a hyperfine field of 550 kOe, associated with M2 sites, and two ferrous patterns with hyperfine fields of 200 and 100 kOe, associated with M1 and M3 sites, respectively. Each ferrous hyperfine field is oriented perpendicular to V zz , the principal component of the electric field gradient, which is negative for both sites: V zz =−2.65 mm/s, η=0.1 for M1 and V zz =−2.9 mm/s, η=0.3 for M3. As in sheet silicates, the field gradients suggest pseudo-trigonal distortions of the ferrous sites symmetry, which stabilize 5 A 1g orbital singlet states.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00309577
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