INFLUENCE OF DISORDER ON THE STATIC CRITICAL-BEHAVIOR IN THE FRUSTRATED FERROMAGNETIC SYSTEM CDCR2(1-X)IN2XS4

We present a study of the static critical properties of CdCr2(1-x)In2x S4 type frustrated ferromagnetic compounds. It was performed by means of both Small Angle Neutron Scattering and Neutron Diffraction techniq ues, which respectively allowed us to investigate the temperature depe ndence of the magnetization fluctuations in the paramagnetic phase, an d of the order parameter close to but below the critical point. For T> T-c, the deduced values of the static critical exponents gamma and nu appeared to be strongly increased by dilution. Surprisingly, the magn etization exponent beta seems to be disorder independent, remaining at a value which is close to the 3D-Heisenberg result.