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Magnetoresistance and Hall effect measurements of Ni to 6 GPa
Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences.
In: Journal of Magnetism and Magnetic MaterialsArticle in journal (Refereed) Submitted
URN: urn:nbn:se:uu:diva-92349OAI: oai:DiVA.org:uu-92349DiVA: diva2:165390
Available from: 2004-10-21 Created: 2004-10-21Bibliographically approved
In thesis
1. Magnetotransport Measurements of Ni Thin Films
Open this publication in new window or tab >>Magnetotransport Measurements of Ni Thin Films
2004 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis presents transverse magnetoresistance (MR) and Hall resistivity measurements of nickel thin films at temperatures between 280 and 455 K and pressures up to 6 GPa. An experimental system was developed for conducting precise magnetotransport measurements using the current reversal and van der Pauw techniques in combination with a 10 T superconducting magnet. Polycrystalline Ni0.985O0.015 thin film samples were manufactured with preexisting point contacts allowing highly reproducible magnetotransport measurements at pressure in the diamond anvil cell (DAC).

The magnetic resistivity above the technical saturation of the magnetization was found to decrease linearly to the highest applied fields, 10 T, while the field derivative, 0.010-0.018 µΩ cm T-1 between 280 and 316 K, increased with temperature and decreased with pressure. The decrease in the magnetoresistance is attributed to spin wave damping of electron-magnon scattering processes at high fields. The magnon mass, 535(14) meV Å2 at 0 K and 0 GPa, determined from longitudinal magnetic resistivity theory is a slightly increasing function of pressure. Correlation between the zero field resistivity and the extraordinary Hall coefficient (EHC) confirmed side jump scattering as the dominant diffusion mechanism at 0 GPa, however, skew scattering was found to become increasingly important with pressure.

The effect of oxygen and pressure on the density of states (DOS) at the Fermi level was investigated through total energy band structure calculations using a periodic supercell of 64 atoms to simulate the sample chemistry. The DOS of Ni0.985O0.015 at the Fermi level was found to increase by 27% at 10 GPa relative to 0 GPa. However, when compared to the results for pure Ni, decreases of 60% and 23% occurred for the corresponding calculations at 0 and 10 GPa. The relative differences in the magnetic resistivity are attributed to competing effects between the DOS, average magnetic moment and magnon mass.

The technique developed for conducting magnetotransport measurements at pressure is applicable to the study of electronic diffusion in ferromagnets as well as geophysical problems such as the geodynamo.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2004. 41 p.
Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1104-232X ; 1037
Earth sciences, magnetoresistance, Hall effect, diamond anvil cell, magnon scattering, band ferromagnetism, nickel, Geovetenskap
National Category
Earth and Related Environmental Sciences
urn:nbn:se:uu:diva-4653 (URN)91-554-6084-4 (ISBN)
Public defence
2004-11-26, Axel Hambergsalen, Geocentrum, Villavägen 16, Uppsala, 10:00
Available from: 2004-10-21 Created: 2004-10-21Bibliographically approved

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