Abstract
Neutron reflectivity studies of EuS/SrS, EuS/PbSe and EuS/PbTe all-semiconductor superlatticeswere carried out in a search for exchange interlayer coupling. A relatively weak antiferromagneticcoupling was found in EuS/SrS and EuS/PbSe systems but no interlayer coupling wasdetected in EuS/PbTe superlattices. In EuS/SrS, where the SrS spacer is an insulator(Eg≈4 eV), a very weak and short range interlayer coupling is in agreement with theearlier theoretical predictions that the interlayer coupling strength in EuS-basedmagnetic semiconductor superlattices depends strongly on the energy gapof the nonmagnetic layer and should decrease with an increase of the energygap of the spacer material. A weak coupling in EuS/PbSe and no couplingin EuS/PbTe, where both PbSe and PbTe are narrow-gap semiconductors(Eg≈0.3 eV), is in disagreement not only with the theoretical expectations but also in starkcontrast with earlier results for another narrow-gap spacer system, EuS/PbS,where pronounced antiferromagnetic coupling persists even in samples with PbSlayer thicknesses as large as 200 Å. A possible influence of the increasing latticemismatch between EuS and the spacer materials (0.5%, 0.8%, 2.5% and 8.2% for PbS,SrS, PbSe and PbTe, respectively) on the magnetic ordering of the EuS layernear the interfaces and, consequently, on the interlayer coupling is discussed.
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