Statistical Theory of Antiferromagnetic Spin Structures in the Rutile Type Crystal with Application to VF2

By applying the method of symmetry breaking potential to the spin system on the rutile type crystal lattice with three sorts of exchange coupling, dependences of the spin structure on those couplings and the temperature are investigated up to the second order approximation. Thus, the phase diagrarn in the space of the exchange couplings and temperature is obtained, in which the phase of helical (screw-type) spin structure predicted by Yoshimori, MnF 2 type structure, and structure suggested by Bizette, Erickson and Yosida appear. For the helical structure, the temperature dependence of the pitch is calculated. The results are in good agreement with the experimental facts on the helical spin structure in the VF 2 crystal.