X-ray-diffraction study of critical phenomena at the spin-Peierls transition in CuGeO3

We have performed x-ray-diffraction measurements of the critical phenomena associated with the spin-Peierls phase transition in CuGeO3. Measurements of the order parameter indicate a value of the critical exponent β of 0.345±0.03 consistent with conventional three-dimensional (3D) behavior and in closest agreement with 3D XY universality, as expected on theoretical grounds. This work also indicates a rather narrow asymptotic critical region …