Magnetic order in the random-field Ising film Fe0.52Zn0.48F2

The extinction-free neutron scattering for a 3.4 mu m epitaxial film of the dilute antiferromagnet Fe0.52Zn0.48F2 has been studied near The (100) antiferromagnetic Bragg point. For the H=0 Bragg scattering we observe the random-exchange Ising model behavior I similar to\t\(2 beta) with beta=0.35. For 0<H less than or equal to 4.5 T the random-field Ising peak intensity vs T has the opposite curvature from the H=0 case near T-c(H). We argue that this has to do with the formation of two weakly interacting, interpenetrating, antiferromagnetically ordered domains with interfaces primarily falling on vacancy sites.