Spin-waves in Antiferromagnetically-Coupled Bimetallic Oxalates

Abstract

Bimetallic oxalates are molecule-based magnets with transition-metal ions M(II) and M�(III) arranged on an open honeycomb lattice. Performing a Holstein-Primakoff expansion, we obtain the spin-wave spectrum of antiferromagnetically-coupled bimetallic oxalates as a function of the crystal-field angular momentum L2 and L3 on the M(II) and M�(III) sites. Our results are applied to the Fe(II)Mn(III), Ni(II)Mn(III) and V(II)V(III) bimetallic oxalates, where the spin-wave gap varies from 0 meV for quenched angular momentum to as high as 15 meV. The presence or absence of magnetic compensation appears to have no effect on the spin-wave gap.