Interlayer coupling betwee layers separated by an insulating nonmagnetic MgO layer

Abstract

The magnetic interlayer coupling between two magnetic layers separated by an insulator was investigated on (Formula presented)(Formula presented)(Formula presented)/(Formula presented)(Formula presented)/MgO/(Formula presented)(Formula presented) samples grown by means of molecular beam epitaxy on (001) (Formula presented)(Formula presented) substrates. The samples were designed to observe interlayer coupling of either sign. Hysteresis loop measurements show that the (Formula presented)(Formula presented) layers are ferromagnetically coupled in the thickness range 0-45 nm MgO. Below a MgO spacer thickness of 1.3 nm, the coupling strength increases drastically with decreasing MgO thickness and is ascribed to the existence of ferromagnetic bridges through the MgO spacer. The small ferromagnetic coupling above 1.3 nm seems to arise from a magnetostatic coupling due to correlated interface irregularities. © 1997 The American Physical Society.