MAGNETIC-PROPERTIES OF RBVF4

The magnetic and electronic properties of RbVF4 have been studied using infrared absorption spectroscopy and neutron scattering techniques. The V+++ ion has in its ground state both orbital and spin angular momentum and so is strongly influenced by the tetragonal and orthorhombic crystal fields. The absorption bands in the infrared have been assigned to transitions between the states of the V+++ ion. The neutron scattering measurements determined the nature of the antiferromagnetic order and the low-temperature excitations. The ground state of the V+++ ions is a doublet which is split by the magnetic ordering at 44 K. The temperature dependence of the order parameter and the behaviour of the excitations suggest that the magnetic interactions are largely confined to the antiferromagnetic sheets. The excitations observed are not associated with the ground doublet but with transitions from the ground state to the next excited state. Values for the crystal field, spin-orbit and exchange parameters are deduced.