Fabrication and Characterisation of Synthetic Antiferromagnetic (SAF) Multilayer Systems.

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The goal of my project is to fabricate and characterise the magneto-transport and magnetometry behaviour of magnetic heterostructures separated by a non-magnetic transition metal (TM) spacer layer. The magnetic layers will be Iron or Galfenol (an alloy of Iron and Gallium) and will be deposited utilising physical vapour deposition techniques (PVD). A range of TM spacers will be utilised and will be characterised to investigate which spacer gives the optimal properties required. The characterisation will utilise a variety of techniques such as SQUID magnetometry, and electrical transport measurements. Memory cells consisting of Ferromagnetic devices are limited by device separation, the limitation arises due to the stray fields emitted by neighbouring cells. SAF's have the advantage of having no net magnetisation at zero field, thus cross talk of devices is eliminated. The advantage of this is that devices density can be increased thus leading to more efficient memory storage. Also, SAFs can also be switched at lower fields than single layer ferromagnets. The advantage of heterostructres with strong interlayer exchange coupling (IEC) is that they will exhibit a large change in the measured resistance during switching due to an effect called the giant magnetoresistance effect (GMR). Galfenol possesses an interesting property called magnetostriction. The magnetostriction for Galfenol is very large compared to Iron and other FM alloys. Magnetostriction is the phenomenon in which a strain applied to the material can alter its magnetic properties. This has previously been studied within heterostructures but in the case where they layers were weakly coupled with no (IEC) present. Galfenol based synthetic antiferromagnetic heterostructures have not previously been studied. And therefore may have the potential to be utilised in conjunction with a piezoelectric material to create a strain controlled spin valve system or provide further advances into memory storage/ magnetic sensor devices.