Anisotropic Effects on Magnetoelastic Transition in Magnetic Molecular Rings

We numerically study the anisotropic effects on the magnetoelastic transition in an S=1/2 XXZ model with a finite lattice number. It is found that the order of the magnetoelastic transition is strongly affected by the anisotropy parameter λ and there may exist a critical λ_c dividing the first-order transition and the continuous transition.