Temperature Dependence of the Spin Waves in ErFe2

The temperature renormalisation of the energies of the optic modes in ErFe2 has been determined from room temperature up to close to the Curie temperature (574K). It is found that the two modes, a dispersive transition-metal mode and a localised crystal-field-dominated mode, cross over at about 420K.

The experimental results have been interpreted and are well accounted for by a linear spin wave model, where the level scheme of the lowest J multiplet of the Er3+ site has been assumed to consist of pure Jz states with an equidistant energy spacing between the levels.