Spin wavesinantiferromagnetically coupled bimetallic oxalates

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 15meV. The presence or absence of magnetic compensation appears to have no effect on the spin-wave gap.