Correlation between interlayer exchange coupling and hydrogen absorption in V-Fe layered structures

Abstract

Abstract 4 nm – Fe/d V -V/4 nm – Fe trilayers were prepared at room temperature using UHV (5 × 10 − 10 mbar) magnetron sputtering. A capping layer of 5 nm Pd was used to allow a fast uptake and release of hydrogen and to avoid oxidation of the top Fe sublayers. As a substrate we have used Si(100) wafers with an oxidised surface. The cleanness and planar growth of all layers was checked in-situ , immediately after deposition by X-ray Photoelectron Spectroscopy. Planar growth was also revealed in ex-situ studies by Atomic Force Microscopy and Scanning Tunnelling Microscopy. In the case of the trilayers the bottom and the top Fe sublayers were deposited in different deposition conditions to obtain relatively high difference in their coercive fields. Interlayer exchange coupling across vanadium was studied for “as prepared”, hydrogenated and dehydrogenated samples using minor hysteresis loop measurements. We have observed the strongest antiferromagnetic (AFM) interlayer exchange coupling energy of about 0.023 mJ/m 2 for hydrogenated sample. Results from the minor hysteresis loop measurements as a function of vanadium layer thickness for “as prepared” or dehydrogenated samples show three AFM peaks near d V ~ 1.95, 2.85, and 3.9 nm without transition to pure ferromagnetic coupling. Hydrogenation of the trilayers changes reversibly the interlayer exchange coupling strength and position of the 2nd and 3rd AFM peak.