School of Physics and Astrophysics

Postgraduate research profiles

Contact

Nicholas Loh

Phone: (+61 2) 9717 7216


Supervisors

Start date

Aug 2006

Submission date

Jul 2010

Nicholas Loh

Thesis

The Magnetism of Co/CuMn multilayers and compressed CrO2: investigations with polarised X-rays and Neutrons

Summary

Polarised x-ray and neutron scattering techniques are a powerful probe of nano-scale magnetic structures and the interactions that govern them. My research involves several projects on this theme. In the first case, coupling between the lattice structure and magnetism in CrO2 is investigated by measuring K-edge X-ray Magnetic Circular Dichroism (XMCD) as a function of pressure. The interplay between the lattice and magnetic properties in transition metal oxides can be rich and varied with many effects like Jahn-Teller distortions, exchange striction, band broadening and orbital quenching all influencing the magnetic state. In CrO2 we have found that there is a quenching of the orbital moment with pressure which has a strong effect on the K-edge XMCD. Secondly, the temperature dependence of the interlayer coupling in Co/CuMn multilayers has been investigated using polarised neutron reflectivity (PNR). In this system the Mn has been doped into the Cu spacer layer causing the Co layers to orienate at right angles to each other at low temperatures. PNR is very sensitive to modulations in magnetic orientation of layers within the multilayer stack, hence measuring PNR as a function of temperuate and field one can build up a detailed picture of the interlayer exchange coupling interactions present in the system.  

Why my research is important

Manipulating the magnetic properties of materials on the nanoscale has significant technological applications as evidenced by the discovery of the Giant-Magneto Resisance (GMR) effect and it subsquent use as in recording technology of hard drives. Understanding how the interlayer exchange coupling works in GMR systems such as Co/CuMn thus represents a useful contribution to knowledge. In the case of CrO2, the work may be of relevence when growing strained films CrO2 for use in spintronic devices.

Funding

  • Externally Funded Scholarship from the Bragg Institute at the Australian Nuclear Science and Technology Organisation (ANSTO)


 

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Last updated:
Monday, 2 August, 2010 2:54 PM

http://www.physics.uwa.edu.au/1023927