Spin-glass state and long-range magnetic order in Pb(Fe1/2Nb1/2)O3 seen via neutron scattering and muon spin rotation

We have investigated the magnetic ground state of the multiferroic relaxor ferroelectric Pb(Fe1/2Nb1/2)O-3 with mu SR spectroscopy and neutron scattering. We find that a transition to a partially disordered phase occurs below T=20 K that coexists with long-range antiferromagnetic ordering. The disordered phase resembles a spin glass. No clustering of magnetic ions could be evidenced by mu SR so that the coexistence appears homogeneous in the sample.