PRESSURE EVOLUTION OF THE EFG AND MAGNETIC HYPERFINE FIELD IN THE LAYERED ANTIFERROMAGNET FEI2

When FeI2 is subjected to pressures of up to 20 GPa, a change of appro ximately 20% occurs in the unit cell volume. Fe-57 Mossbauer spectrosc opy (MS) in a diamond-anvil cell has been used to monitor the pressure evolution of the hyperfine interaction parameters of this layered ant iferromagnetic insulator. The pressure dependence of the quadrupole sp litting QS at 296 K exhibits a maximum at similar to 12 GPa and the sa turation magnetic hyperfine field H-0 increases from 7.4 T at ambient pressure to 12 T at 18 GPa. A qualitative analysis identifies the pres sure evolution of QS with changes in the trigonal component of the cry stal field splitting. The pressure variation of Ho is attributed to an increase in the average value of the 3d charge density distribution.