Structures and magnetism of alkali tetrafluoromanganates(III)

P161

411

STRUCTURES

AND MAGNETISM

OF ALKALI TETRAFLUOROMANGANATES(lll)

M.Molinier, W.Massa, Fachbereich Chemie und WZMW der Universitat Hans-Meerwein-Str., D-3550 Marburg, Germany

Marburg,

S.Khairoun, A.Tressaud, Laboratoire de Chimie du Solide du CNRS, 351, tours de la Liberation, F-33405 Talence, France A.Boireau,

J.L.Soubeyroux,

The AMnF, structures

compounds

layers.

properties

x-superexchange

Although

and of the concurring

interactions

dependent

were determined

our single crystal investigations

France

have Jahn-Teller-distorted

Thus, the compounds

most of these compounds

tailed crystal structures

BP 156 X, F-38042 Grenoble,

(A = alkali atom)

deriving from the TIAIF, type.

for studies of 2D magnetic romagnetic

lnstitut Laue-Langevin,

layered

are interesting

ferromagnetic

on the bridge

models

u- and antifer-

angles

within the

are known since several years (1,2) the de-

only for the LiMnF, compound

recently

(3). In

we found that the different size of the alkali counter

cat-

ions gives rise to three different structure variants: 1.

NaMnF,,

isotypic with LiMnF, (3), space group P2, /c, a = 573,6(2),

b = 489,2(i), 2. 3.

KMnF,,

c = 574,8(2) pm, 8 = 108.07(2)0 (see fig. below).

space group P2,/a,

a = 769.9, b = 764.4, c = 576.9 pm, 8 = 90.54O.

RbMnF,,

isotypic, a = 780.6, b = 776.6, c = 604.6 pm, 8 = 90.69O.

CsMnF,,

space

group

twins, seeming P4/nmm

P4/n,

a = 794.4, c = 633.8 pm, merohedral

Other variants are found for the corresponding The structural type of the [MnF,]magnetic properties,

(110)

space group (2). TI (4) and NH, (5) compounds.

classes differ in the Mn-F-Mn bridge angles and in the puckering

layers.

The correlations

investigated

between

these geometric

by magnetic measurements

features

and the

and neutron diffraction,

discussed. References P.KGhler, W.Massa, D.Reinen. B.Hofmann und R.Hoppe, Z.anorg.allg.Chem. 446,131 (1978) W. Massa and M. Steiner, J. Solid State Chem. 32, 137-143 (1980) K. H. Wandner and R. Hoppe, Z. Anorg. Allg. Chem. 546, 113-121 (1987). P.NuAez, A.Tressaud, J.Grannec, P.Hagenmuller, W.Massa, D.Babel, A.Boireau and J.L.Soubeyroux, Z.Anorg.Allg.Chem., in press W.Massa, Inorg.Nucl.Chem.Lett. 13, 253 (1977); M.Molinier, W,Massa, single crystal investigation in progress

are