Temperature-induced antiferromagnetic interlayer exchange coupling in (Ga,Mn)(As,P)-based trilayer structure

We present the observation of temperature-induced transition between ferromagnetic (FM) and antiferromagnetic (AFM) interlayer exchange coupling (IEC) in trilayer structures consisting of two (Ga,Mn)(As,P) ferromagnetic layers and a GaAs:Be spacer. Hall resistance measurements were performed on trilayers prepared in as-grown and annealed states. Anomalous Hall resistance (AHR) measurements show two-step hysteresis loops, indicating that coercive fields of the two (Ga,Mn)(As,P) layers in the trilayer are different. Minor loops of AHR show characteristic shifts that correspond to FM IEC at low temperatures and AFM IEC at high temperatures in both as-grown and annealed samples. This temperature-induced transition from FM to AFM IEC occurs at a lower temperature in the annealed sample than in the as-grown sample. We attribute such an enhanced IEC transition effect in the annealed sample to the increase of carrier concentrations obtained by annealing, a characteristic feature of ferromagnetic semiconductors. The observation of AFM IEC in the (Ga,Mn)(As,P)-based trilayer suggests the possibility of realizing synthetic antiferromagnetic systems in such structures, which can be used for antiferromagnetic spintronic device applications.