Hydrogen in ultrathin vanadium layers
1999 (English)Doctoral thesis, comprehensive summary (Other academic)
The influence of elastic boundary conditions on the thermodynamics of hydrogen in vanadium were investigated using resistometry, x-ray diffraction and nuclear reaction analysis. To provide varying lattice strain states Mo/V (110) and Fe/V (001) superlattices with thickness L of individual layers in the range 3-16 monolayers (ML) were used. In addition the thickness ratio LFe/LV in the latter samples was varied. The results were compared with earlier work on Mo/V (001) superlattices.
In the Mo/V (110) superlattices the H-H interaction was found to be repulsive in contrast to the (001) oriented samples and bulk V. This was also the case for Fe/V (001). For the thickness ratios LFe/LV = 3/10 and 3/16 it was found that the hydrogen-depleted interface region in V was populated at lower average concentration than in the symmetric samples (LFeLV = 1). This was related to the decreased Fe thickness.
For Fe(3ML)/V(12-15 ML) samples the effects of hydrogenation on the magnetic exchange coupling between the Fe layers were investigated using neutron reflectometry. For 12 and 14 ML of V the coupling was switched continuously from antiferromagnetic (AFM) to ferromagnetic (FM) upon introduction of small amounts of hydrogen, whereas the initially FM-coupled 15-ML sampleexhibited an antiferromagnetic "resonance" at H/V ≈ 0.02. This was found to be due to changes in the vanadium Fermi surface. An intermediate state of noncollinear coupling was also observed in the 14-ML sample.
Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis , 1999. , 49 p.
Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1104-232X ; 442
Research subject Physics
IdentifiersURN: urn:nbn:se:uu:diva-1231ISBN: 91-554-4425-3OAI: oai:DiVA.org:uu-1231DiVA: diva2:160790
1999-05-21, lecture room 2001, Ångström laboratory, Uppsala University, Uppsala, 10:15