  The critical exponent beta =0.16 +- 0.02 for the random-field Ising model
order parameter is determined using extinction-free magnetic x-ray scattering
for Fe(0.85)Zn(0.15)F2 in magnetic fields of 10 and 11 T. The observed value is
consistent with other experimental random-field critical exponents, but
disagrees sharply with Monte Carlo and exact ground state calculations on
finite-sized systems.
