90°coupling in (Fe/Cr/Fe)AFM/Cr/Fe system epitaxially grown on GaAs(001)

Single-crystalline (Fe/Cr/Fe)(AFM)/Cr/Fe structures were epitaxially grown on atomically flat GaAs(0 0 1). Choosing the same thickness of the antiferromagnetically (AFM) coupled Fe layers in the bottom (Fe/Cr/Fe)AFM structure, their net magnetization is balanced to zero, in particular up to a spin-flop transition when the field is applied along the [I 10] direction. For the Cr thicknesses at which the top Fe layer is weakly magnetically coupled to the bottom (Fe/Cr/Fe)AFM structure, at low fields, the magneto-optical Kerr effect and/or SQUID signal from the sample corresponds to the top Fe layer only. An influence of the Cr spin structure on the magnetization reversal in the Fe layer is reported. In particular, a strong increase of coercivity (by a factor of 12) is found at low temperatures. A 90degrees coupling is detected which affects the minor loops measured along the [-1 1 0] and [1 0 0] directions. (C) 2004 Elsevier Ltd. All rights reserved.