Antiferromagnetic phase transition inCd1−xMnxSe epilayers

Neutron-diffraction spectra of molecular-beam-epitaxy-grown single-crystal zinc-blende films of ${\mathrm{Cd}}_{1\mathrm{-}\mathit{x}}$ ${\mathrm{Mn}}_{\mathit{x}}$Se reveals the onset of type-III antiferromagnetic ordering (AFM-III) for x=0.70 and 0.75 at a sharp Néel temperature. The AFM-III order is long range, with correlation lengths of around 400 Å, and the transition is of second order. This contrasts sharply with earlier studies of bulk ${\mathit{A}}_{1\mathrm{-}\mathit{x}}^{\mathrm{II}}$ ${\mathrm{Mn}}_{\mathit{x}}$ ${\mathit{B}}^{\mathrm{VI}}$ diluted magnetic semiconductors, where only short-range AFM-III correlations are observed, evolving gradually with decreasing temperature, and saturating at correlation length values less than 70 Å.