Co2MnSi Heusler alloy thin films
type: CreativeWork
description: This thesis investigates the growth of intermetallic compounds by co-sputtering from single elemental targets. The preliminary work involved constructing a sputtering set-up to grow a binary alloy (Sm-Co) and investigating how to control the composition spread that was obtained. Having achieved this, a larger sputtering flange was built up to grow the ternary Heusler alloy, Co2MnSi. Co2MnSi has been predicted to be a half-metallic ferromagnet, which means that there is an energy gap in the minority spin band at the Fermi energy. This leads to 100 % spin polarised conduction electrons, which would enable ideal spin-device performance to be obtained. Co2MnSi is particularly promising because it is predicted to have a large energy gap in the minority band of ~0.4 eV and has the highest Curie temperature among the known Heuslers of 985 K. Initially, Co2MnSi was grown on a-plane sapphire and stoichiometric films were single phase and highly (110) textured, without the use of a seed layer. They exhibited the bulk value of the saturation magnetisation, Ms and films grown at the highest deposition temperature (715 K) showed the lowest resistivity (47 µΩcm at 4.2 K) and the lowest room temperature coercivity (18 Oe). The spin polarisation of the transport current, Pt of a 400 nm film grown at this deposition temperature was 54 %, consistent with measurements on bulk single crystals. Ms decreased with decreasing film thickness indicating a graded disorder. By growing on GaAs (001), which has a similar lattice parameter to Co2MnSi it was expected that this disordered region would be confined to the first few atomic layers. However, this was not the case because interfacial reactions resulted in the formation of an epitaxial Mn-As region, and a thin interfacial layer that was Co-Ga rich. This prevented the lattice matching of the Co2MnSi to the GaAs(001) hence hindering epitaxial growth of the Heusler. The reaction zone also meant that films exhibited a Ms slightly below the bu…
abstract: This thesis investigates the growth of intermetallic compounds by co-sputtering from single elemental targets. The preliminary work involved constructing a sputtering set-up to grow a binary alloy (Sm-Co) and investigating how to control the composition spread that was obtained. Having achieved this, a larger sputtering flange was built up to grow the ternary Heusler alloy, Co2MnSi. Co2MnSi has been predicted to be a half-metallic ferromagnet, which means that there is an energy gap in the minority spin band at the Fermi energy. This leads to 100 % spin polarised conduction electrons, which would enable ideal spin-device performance to be obtained. Co2MnSi is particularly promising because it is predicted to have a large energy gap in the minority band of ~0.4 eV and has the highest Curie temperature among the known Heuslers of 985 K. Initially, Co2MnSi was grown on a-plane sapphire and stoichiometric films were single phase and highly (110) textured, without the use of a seed layer. They exhibited the bulk value of the saturation magnetisation, Ms and films grown at the highest deposition temperature (715 K) showed the lowest resistivity (47 µΩcm at 4.2 K) and the lowest room temperature coercivity (18 Oe). The spin polarisation of the transport current, Pt of a 400 nm film grown at this deposition temperature was 54 %, consistent with measurements on bulk single crystals. Ms decreased with decreasing film thickness indicating a graded disorder. By growing on GaAs (001), which has a similar lattice parameter to Co2MnSi it was expected that this disordered region would be confined to the first few atomic layers. However, this was not the case because interfacial reactions resulted in the formation of an epitaxial Mn-As region, and a thin interfacial layer that was Co-Ga rich. This prevented the lattice matching of the Co2MnSi to the GaAs(001) hence hindering epitaxial growth of the Heusler. The reaction zone also meant that films exhibited a Ms slightly below the bu…
author: Singh, Laura Jane
language: en
keywords: Heusler Alloy, Spintronics, Thin Films, Half Metallic Ferromagnet
license: https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/5cd5928a-d0a4-4964-b218-9849933e2aff/download
license: https://www.rioxx.net/licenses/all-rights-reserved/
date published: 2005-03
date modified: 2026-07-22T22:24:31Z
provider: Cambridge University
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of Cambridge

PropertyValue
property ID: DOI
value: 10.17863/CAM.14204