Hydrogen-controlled interlayer exchange coupling in Fe/LaHx multilayers

Magneto-optic Kerr magnetometry and neutron reflectometry reveal that Fe la yers exhibit magnetic exchange coupling through LaHx spacer layers. Ferroma gnetic and antiferromagnetic coupling is observed on multilayers of these m aterials depending on the thickness of the hydride layers, but without osci llatory behavior. Starting from metallic La dihydride spacer layers the eff ect of dissolving increasingly more hydrogen was examined. Sign and value o f the coupling depend crucially on the hydrogen content x. The coupling can be inverted from antiferromagnetic to ferromagnetic and vice versa. These alterations are due to modifications of the electronic structure of the hyd ride. When the hydrogen absorption saturates the hydride layers become insu lating and the exchange coupling is likely to disappear. In this final stat e the multilayers are always characterized by a very soft ferromagnetic rec tangular hysteresis curve. Upon removal of the hydrogen to the initial conc entration the original magnetic structure is restored. (C) 2001 Elsevier Sc ience B.V. All rights reserved.