Bull. Minéral.
(1988), 111, 143-147
Electron paramagnetic resonance of a new Fe3+ centre in cassiterite
by Régine RUCK*, Yves DUSAUSOY* and Jean-Marie GAITE**
* Laboratoire de minéralogie et cristallographie, Université Nancy I, U.A. 809, B.P. 239, 54506 Vandœuvre-les-Nancy Cedex, France.
** Laboratoire de cristallographie, Université d'Orléans, U.A. 810, B.P. 6759, Rue de Chartres,
45067 Orléans Cedex 2, France.
Résonance paramagnétique électronique d'un nouveau centre du Fe�+ dans la cassitérite.
Introduction
The impurity centre Fe3+ in Sn02 has been the subject of numerous EPR studies. Five Fe3+ paramagnetic centres were identified and charac¬ terized by the value of "k = B?/3B� ; SN k = 0.115, Il X = 0.037, 12 X = 0.065, Sdl X = 0.314, Sd2 X = 0.253.
Different authors have determined the local symmetry of each centre and proposed charge compensation mechanisms resulting from the substitution of Sn4+ by Fe3+ (Nakada et al., 1966 ; Sperlich, 1968 ; Hou and Tucker, 1969 ; Rhein and Rosinski, 1972 ; Bartkowski and Tunheim, 1972 ; Rhein, 1972 ; Dusausoy et al., 1987).
A new Fe3+ centre, called Sd3, has been re¬ vealed by the EPR study of a natural cassiterite.
According to its crystal field symmetry and its fine structure constants, it is similar to the Sd2 centre identified by Calas and Cottrant in 1982 in powder spectra and studied in single crystal by Dusausoy et al. (1987).
Structure of SnO2
Sn02 is tetragonal with space group />42/ mnm. The tin atoms are six fold coordinated by oxygens with mmm site symmetry. When Fe3+ substitutes Sn4+, these paramagnetic centres are crystallographically equivalent but magnetically non equivalent when the external magnetic field is not parallel to c". The interatomic metal-oxygen distances are 2.056(7) A in the direction [1J0] and 2.052(5) Â in the equatorial plane (1 10) (Bauer, 1956). In the equatorial plane, the
(?) Société française de Minéralogie et de Cristallographie., Paris, 1988.
