Crystal structure of Li2TbF6 and magnetic study under high magnetic Field

66

CRYSTAL STRUCTURE OF Li,TbF, HIGH MAGNETIC FIELD D. Avignant. Laboratoire

M. El-Ghozzi, de Chimie

AND MAGNETIC

STUDY UNDER

J. C. Cousseins

des Solides,

Universite

Blaise Pascal. 63 177 Aubiere

(France)

Y. Laligant,

A. Le Bail, C. Ferey

Laboratoire des Fluorures, UA 449, FacultC des Sciences, 720 17 Le Mans CCdcx (France)

route de Laval,

and M. Guillot Laboratoire

Louis N&l, CNRS, 38042

The crystal X-ray

and

structure

neutron

powder

lizes in the monoclinic a = 7.585(l)

diffraction system,

at

and

5 K using

This compound

crystal-

was solved ab-initio data

respectively.

space group PZ,/C

300

(n" 14), 2 = 4, with

1, c = 11.116(l) 1 and B = 106.96(l)'

at 300 K.

and Rietveld

Li TbF6 exhibits a completely new structural 42 in bicapped trigonal prisms. Lithium ions with Tb

techniques.

compounds

in this structure

(France)

was solved and refined using direct methods

refinement

type for A2MF6

unusual

of Li2TbF6

i, b = 4.965(l)

The structure profile

Grenoble

adopt two types of coordination

square pyramids.

Relationships

polyhedra

with y-Na2UF6

: octahedra and

and CaTa206

structural

types will be presented. The saturation

magnetization

measured

in a 200 kSe magnetic

field at

4.2 K has been found to be equal to 6.9 pR, what provides confirmation 3+ 4+ of the terbium which is isoelectronic with Gd and exhibits

degree

ground

a 8S

712

state.

The Curie law is not found to be obeyed viour will be discussed ground

of the

in terms of magnetic

state level in zero-field.

at low temperatures. interactions

This beha-

or splitting

of the