Quadrupole Hyperfine Interaction and Magnetic Hyperfine Field in FeOCl and Its Intercalates
- PDF / 304,329 Bytes
- 6 Pages / 415.08 x 633.6 pts Page_size
- 62 Downloads / 216 Views
509
QUADRUPOLE HYPERFINE INTERACTION AND MAGNETIC HYPERFINE FIELD IN FeOCI AND ITS INTERCALATES
Y. MAEDA Department of Chemistry, 33 Hakozaki Higashi-Ku,
Faculty of Science, Kyushu University, Fukuoka 812 Japan
R. H. HERBER Department of Chemistry,
Rutgers University,
New Brunswick,
N.J.
08903 USA
ABSTRACT FeOCI is
a layered compound belonging to the orthorhombic
space group Pmnm (D13),
with two formula units per unit cell.
Adjacent layers in the (010) crystallographic plane, in which chlorine atoms face each other, are held together by van der Waals forces which are readily disrupted by the insertion of appropriate Lewis base molecules. This intercalation of 'guest" species causes an expansion in the bdirection, leaving the remainder of the unit cell dimensions unchanged. Among base molecules which are readily intercalated are NH3 , pyridine and a wide variety of substituted pyridines, nitrogen containing heterocyclic molecules, phosphines and phosphites. The limiting stoichiometry ranges from 1:3 ("guest" to Fe atom ratio) for small intercalants to 1:6 for large "guest" molecules. Using both powder X-ray 7 diffraction and temperature dependent ' Fe Mossbauer effect spectroscopy, the lattice dynamics, hyperfine interactions, magnetic ordering temperature and magnetic hyperfine field (at 4.2 K) have been studied for the neat matrix and a number of base intercalates. The magnetic hyperfine field at the iron atom at 4.2 K is 44143 KOe, independent of the magnitude of the b-axis expansion. Vzz is negative for neat FeOCl and intercalates in which the "guest" to host ratio is < 1:3, and positive when this ratio is > 1:4.
Supported by the National Science Foundation under Grant DMR 7808615AO1.
510 INTRODUCTION Iron(III) oxychloride, FeOCI, is a lamellar compound belonging to the orthorhombic space group Pmnm (Dxh) in which two formula units, each containing a high spin iron atom, are present per unit cell [1, 2]. The crystal structure consists of a stack of double sheets of cis-FeCl 2 04 octahedra, linked together with shared edges. The unit cell dimensions of the virgin material are a= 3.780, b= 7.917 and c= 3.302 R, and are readily obtained from the appropriate powder pattern X-ray diffraction data. The lamellar architecture of the matrix has a number of interesting chemical and solid state consequences, among which is the ability to introduce by relatively mild chemical means, a number of organic molecules into the structure [3-7]. These molecules are assumed to insert into the van der Waals layer which is formed by the facing sheets of chlorine atoms, and which is envisioned as being held together by relatively weak chemical forces. The basis of this assumption rests in part on the observation that molecular intercalation into FeOCl causes a marked b-axis expansion, leaving the a and c dimensions of the unit cell nearly intact. The molecules which have been introduced into this lattice are all Lewis base type compounds, although the presence of a lone pair of electrons must be viewed as a necessary, ra
Data Loading...
