Date of Award


Degree Type


Degree Name

Doctor of Philosophy (PhD)




M.F. Collins


Two of the magnetic properties of antiferromagnet, CsMnF₃, were studied by thermal neutron scattering techniques.

Spin wave-dispersion curves, along the two high symmetry directions (00ξ) and (ξ00), were determined and were satisfactorily fitted to a theoretical model with two nearest neighbour exchange constants, J₁₂ = 0.134±.003 THz and J₂₃ = 0.094±.0105 THz, and one second nearest neighbour exchange constant, J₃₅=-0.0138±.003 THz. The spin wave properties can be described in terms of an effective anisotropy field of -2700±900 Oe along the crystal c axis. This field constrains the spins to the basal plane of the crystal. The calculations show that magnetic dipole-dipole interactions, alone, provide enough anisotropy to account for the observed results.

The sublattice magnetization, over the temperature range of 6.8 K to 72.2 K, was measured. This shows a critical phase transition with a critical exponent β given by β = 0.317±.009.

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