Spin wave excitations in kagome staircase Co$_3$V$_2$O$_8$

Co$_3$V$_2$O$_8$ features spin-3/2 moments decorating a buckled kagome staircase lattice. While the ground state is a collinear ferromagnet, the $H-T$ phase diagram features a complex series of transversely polarized spin density wave states with a variable propagation vector that takes on multiple distinct commensurate and incommensurate values. The spin wave dispersion within the ($0\,K\,L)$ plane in the ferromagnetic phase has been fully mapped out using the DCS time-of-flight neutron spectrometer. While previous work has treated this compound as a quasi-two dimensional structure of weakly coupled kagome lattice planes we have measured significant spin wave dispersion along the $b$-axis, indicating a three dimensional lattice with significant coupling between the buckled kagome planes.