Development of a Surface Magneto-Optic Kerr Effect Setup

Student thesis: Master Thesis and HD Thesis

  • Kristian Bonderup Pedersen
  • Rasmus Bjørn
4. term, Nanotechnology, Master (Master Programme)

Interest in magnetic nanostructures has increased together with the technological progress. Application of magnetic nanostructeres in e.g. hard disk drives and as magnetic sensors is one of the reasons for increasing demands on size and control of the reorientation of magnetic moments. Based on this a versatile method for characterizing magnetic nanostructeres is essential. The magneto-optic Kerr effect has been used for decades in magnetic analysis, and by combining this concept with a UHV chamber one obtains a surface sensitive method for characterizing magnetic properties of structures in the monolayer range. Accordingly the primary objective of this project is to develop a setup utilizing the surface magneto-optic Kerr effect and adapt it to an existing UHV chamber. Secondly the setup is validated through surface magneto-optic Kerr effect measurements on Co thin films. 
Generally the project is separated in three parts: introductory theory, design and development, and finally validation of the system through Kerr effect measurements on Co thin films.
The introductory theory contains the knowledge necessary in order to understand the concept of magneto-optic kerr effect and the magnetic properties of thin films. Initially the basic concepts of magnetism are defined through a semi-classical and statistical mechanical approach. Afterwards magnetism in systems of reduced dimensions, more specifically thin films, is regarded using anisotropy considerations.
Finally the concept of magneto-optic Kerr effect is discussed and a setup utilizing the effect for magnetic probing is presented.
It is desired to adapt the surface magneto-optic Kerr effect setup to an existing vacuum system already containing a vaporizer, mass spectrometers, LEED, and a STM. To ease the design of the system, a preliminary simplfified surface magnetooptic Kerr setup is fabricated outside of vacuum. This setup is also used to validate the method as a means to characterize magnetic properties. During the development of the main setup several concepts were considered, the primary are presented chronologically with regard to when they were considered along with pros and cons of the idea. Finally the blueprints for the components designed are presented for the entire final setup.
The final setup comprises numerous components and applications. Overall the setup is centered around a custom designed electromagnet able to deliver app. 200mT in a polar and longitudinal configuration. Furthermore the addition of a cryostat enables cooling to -183°C for sample characterization at lowered temperatures. Through Kerr effect measurements various deficiencies in the setup are identified, e.g. problems with: the entrance windows to the chamber and large order intensity drift. Inspite of this a hysterisis loop is recorded for Co deposited on Ag(111).

Publication date1 Jun 2011
Number of pages138
ID: 53271878