Spontaneous Hall effect in MBE grown Fe layers on GaAs(311) and GaAs(331) substrates

The spontaneous Hall effect in Fe layers epitaxially grown on GaAs(3 1 1)A and GaAs(3 3 I)A substrates is utilised to characterise the electronic and magnetic properties of the layers. We observe a very unusual hysteresis behaviour, which arises from the in-plane magnetisation with the easy axes along the [233] and [110] direction fur the GaAs (3 1 1)A and GaAs(3 3 1)A substrates, respectively. A non-vanishing transverse magnetoresistance appears even for in-plane magnetic fields. We identify the origin of the non-vanishing transverse magnetoresistance as the spin-orbit interaction between conducting electrons and impurities. Different models, including out-of-plane magnetisation of the Fe-layers grown on high index GaAs substrates due to the stepped heterointerface and spin-orbit interaction governed by the magneto-crystalline anisotropy of bulk Fe or of the heterointerface, are discussed to explain the unusual 'in-plane Hall effect'. (C) 2001 Elsevier Science B.V. All rights reserved.