ENDOR investigation of the structural phase transition in RbCdF3

Abstract
The structural phase transition in RbCdF3 at 124K from cubic to tetragonal symmetry was studied by investigating the paramagnetic Mn2+ and Fe3+ probes with ENDOR. From the superhyperfine interactions the order parameter could be inferred. It is shown that the phase transition is weakly of first order. The lattice relaxation about the probe causes the order parameter to be a 'local' one, which differs from first to third shell of neighbours around the probe ion. The results demonstrate the limitations of the use of probes to study the intrinsic crystal properties.