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

我的项目目标是制造和表征由非磁性过渡金属（TM）间隔层分隔的磁异质结构的磁输运和磁强计行为。磁性层将是铁或Galfenol（铁和镓的合金），并将利用物理气相沉积技术（PVD）沉积。将使用一系列TM隔离剂，并对其进行表征，以研究哪种隔离剂能提供所需的最佳性能。表征将利用各种技术，如SQUID磁强计和电输运测量。由铁磁器件组成的存储单元受到器件分离的限制，这种限制是由相邻单元发出的杂散场引起的。SAF的优点是在零场处没有净磁化，从而消除了器件的串扰。这样做的好处是可以增加设备密度，从而导致更有效的内存存储。此外，saf也可以在比单层铁磁体更低的场中切换。具有强层间交换耦合（IEC）的异质结构的优点是，由于巨磁阻效应（GMR）的影响，它们在开关过程中会表现出很大的测量电阻变化。Galfenol有一个有趣的特性，叫做磁致伸缩。与铁和其他FM合金相比，Galfenol的磁致伸缩非常大。磁致伸缩是施加在材料上的应变可以改变其磁性质的现象。这在以前的异质结构中已经研究过，但在它们层弱耦合而没有（IEC）存在的情况下。以Galfenol为基础的合成反铁磁异质结构以前还没有研究过。因此，它可能有潜力与压电材料结合使用，以创建应变控制的自旋阀系统，或进一步发展为内存存储/磁传感器设备。

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.