Field‐induced ’’exchange flips’’ in a randomly diluted antiferromagnet (invited)

High field magnetization measurements of the randomly diluted, anisotropic antiferromagnet FexZn1−xF2 have revealed the behavior of novel single‐spin ’’exchange‐flips’’ as well as the concentration‐dependent spin‐flop field HSF. Measurements were made in pulsed field up to 550 kOe in the High Magnetic Field Laboratory in Osaka University on samples from pure FeF2 to beyond the percolation limit. The exchange flips occur when the applied field H0 exceeds the effective exchange field HE = nHE/z at sites on the down‐sublattice with n magnetic neighbors. Below either HSF or a ’’crossover’’ field Hcr, hysteretic behavior is seen with respect to the direction of field sweep, whereas above HSF or Hcr it is absent. Further, Hcr is marked by an anomalous peak in dM/dH versus H0. These effects are explained by a transition to a disordered state above Hcr, which possesses no long‐range antiferromagnetic order. A classical‐spin computer simulation has been found to accurately reproduce these effects.

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