Magnetoresistive sensors for magnetic domain wall technologies
Lead Research Organisation:
University of Sheffield
Department Name: Materials Science and Engineering
Abstract
Recent developments in magnetic nanotechnology have seen new device concepts emerge that could challenge traditional silicon-based microelectronics in certain applications. A key advantage of magnetic devices over alternative technologies is that they generally do not require power to retain data. In specific cases, magnetic nanotechnology devices may also offer higher device density, lower power consumption, improved reliability or additional functionality compared with their rivals. Some of these magnetic devices are made using thin ferromagnetic layers separated by a non-magnetic metal spacer layer just a few atoms thick. The upper and lower layer will have different magnetisation directions and the electrical resistance of the overall device depends on their relative orientation due to an effect known as 'giant magnetoresistance' (GMR). Already, these devices are widely used as magnetic field sensors in many applications, e.g. in computers and automotive products. Other technologies are being developed based upon networks of planar magnetic nanowires, usually with just a single magnetic layer and no spacer layers. The geometry of the wires is important, since this restricts magnetisation to lie in one of two directions along the wire axis. This provides a simple system for representing the binary numbers of digital information. Opposite magnetisation directions can meet, and where this happens, they are separated by a transition region known as a 'domain wall'. Domain walls can be easily created or removed and made to propagate through a nanowire network using magnetic fields or electrical currents in the nanowires. In this way, information is written, deleted and sent through a circuit, be it a sensor, memory or logic device. However, for these devices to be commercially successful, we must have read-out of the magnetic data in form compatible with modern electronics. There have not been any demonstrations of this to date. In this collaborative research programme, we will address this deficiency by developing a nanoscale device to read data in magnetic nanowires. Our recent calculations have shown that the magnetic field from domain walls is very high close to the nanowires. We will use this field to change the magnetic configuration of a nearby sensor and detect these changes using GMR. This will be a significant step for magnetic nanowire technologies since it will allow nanowire devices to be fully integrated as stand-alone integrated circuits. We will also use these sensors for scientific measurements to improve our understanding of the behaviour of domain walls in magnetic nanowires.The applicants for this project bring together world-leading experience in nanofabrication, magnetic nanowires, GMR materials and computer modelling of nanoscale magnetic systems, making this the ideal team to undertake such a challenging project.
Publications
Bashir M
(2012)
Head and bit patterned media optimization at areal densities of 2.5Tbit/in2 and beyond
in Journal of Magnetism and Magnetic Materials
Bashir M
(2011)
Remote domain wall chirality measurement via stray field detection
in Journal of Applied Physics
Bryan M
(2012)
Dynamics of stress-induced domain wall motion
in Physical Review B
Bryan M
(2012)
Stochastic switching asymmetry in magnetoresistive stacks due to adjacent nanowire stray field
in Applied Physics Letters
Bryan MT
(2012)
Transverse and vortex domain wall structure in magnetic nanowires with uniaxial in-plane anisotropy.
in Journal of physics. Condensed matter : an Institute of Physics journal
Dean J
(2010)
The incorporation of the Cauchy stress matrix tensor in micromagnetic simulations
in Journal of Applied Physics
Dean J
(2011)
Stress-based control of magnetic nanowire domain walls in artificial multiferroic systems
in Journal of Applied Physics
Hayward T
(2010)
Pinning induced by inter-domain wall interactions in planar magnetic nanowires
in Applied Physics Letters
Hayward T
(2010)
Direct imaging of domain-wall interactions in Ni 80 Fe 20 planar nanowires
in Physical Review B
Hrkac G
(2011)
Nanowire spintronics for storage class memories and logic
in Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences
Description | This project sought to investigate how the magnetic field emanating from nanostructures interacts with adjacent magnetic field sensors. In particular, we investigated the stray field from patterned ferromagnetic nanowires and from domain walls in these nanowires. The sensor we focussed on was a patterned giant magnetostrictive spin valve. Our findings were: - Calculations showed spin valve sensors can sense the presence and structure of a domain wall in a nearby nanowire. - Experiments and calculations demonstrated sensing of magnetisation switching in a nanowire using the giant magnetoresistive signal of a patterned spin valve. We were also able to investigate other nanowire memory systems as part of this project. The main findings of this were: - Stress gradients along a magnetostrictive (stress-sensitive) nanowire can be used as a low-energy means of moving and positioning magnetic domain walls. When using a piezoelectric substrate to generate the stress, the presence of a domain wall can also be detected from an induced voltage in the substrate. - By incorporating a full stress tensor into a micromagnetic finite element model we were able to show how (often substrate-induced) surface stress affects the magnetic properties of thin films. |
Exploitation Route | Integration of magnetoresistive sensors in magnetic nanowire technologies |
Sectors | Digital/Communication/Information Technologies (including Software) |
Description | EPSRC Impact Acceleration Account (IAA) |
Amount | £40,391 (GBP) |
Funding ID | Internal reference 139495 as part of EPSRC Impact Acceleration Account award EP/K503812/1 |
Organisation | Engineering and Physical Sciences Research Council (EPSRC) |
Sector | Public |
Country | United Kingdom |
Start | 05/2014 |
End | 09/2015 |
Description | EPSRC Impact Acceleration Account (IAA) |
Amount | £50,000 (GBP) |
Organisation | Engineering and Physical Sciences Research Council (EPSRC) |
Sector | Public |
Country | United Kingdom |
Start | 05/2014 |
End | 09/2015 |