Thermal enhancement of the antiferromagnetic exchange coupling between Fe epilayers separated by a crystalline ZnSe spacer

J. VARALDA,J. MILANO, A. J. A. DE OLIVEIRA, E. M. KAKUNO, I. MAZZARO, D. H. MOSCA, L.B. STEREN, M. EDDRIEF, M. MARANGOLO, D. DEMAILLE, V. H. ETGENS

JOURNAL OF PHYSICS CONDENSED MATTER

Institut of Physics Publishing

Año: 2006 vol. 18 p. 9105 - 9118

0953-8984

We provide evidence for the existence of an antiferromagnetic coupling between iron epilayers separated by a wedge-like ZnSe crystalline semiconductor by magnetometric and ferromagnetic resonance experiments. The coupling strength of 46 µJ m-2 for tZnSe = 25 Å is strongly reduced as the barrier thickness is increased. The coupling increases linearly with temperature from 5 to 300 K, with a 5.5 × 10-9 J m-2 K-1 rate. Thermally induced effective exchange coupling mediated by spin-dependent tunnelling of electrons via localized mid-gap defect states in the ZnSe spacer layer appears to be the most plausible mechanism to induce the antiferromagnetic coupling.