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Details of Grant 

EPSRC Reference: EP/L000121/1
Title: Experimental implementation of a novel spintronic concept
Principal Investigator: Hindmarch, Dr AT
Other Investigators:
Researcher Co-Investigators:
Project Partners:
Open University
Department: Physics
Organisation: Durham, University of
Scheme: First Grant - Revised 2009
Starts: 31 January 2014 Ends: 30 January 2016 Value (£): 93,150
EPSRC Research Topic Classifications:
Magnetism/Magnetic Phenomena
EPSRC Industrial Sector Classifications:
Related Grants:
Panel History:
Panel DatePanel NameOutcome
23 Apr 2013 EPSRC Physical Sciences Physics - April 2013 Announced
Summary on Grant Application Form
Magnetic thin-film sensors have played a pivotal role in producing the massive increase in digital data storage capacity in recent decades, enabling the digital revolution which defines modern society, and are the primary commercial application of the research field known as 'spintronics'. In spintronics the quantum-mechanical angular momentum, or spin, of the electron is used as a two-state variable for encoding, transporting, manipulating, and sensing digital information. Since the advent of spintronics hard disk readback sensors evolved through several generations of `magnetoresistance' technology. Magnetoresistance describes a large change in electrical resistance in response to a magnetic field which encodes data onto the disk. The current state-of-the-art device is a planar structure consisting of two magnetic layers separated by an insulating layer less than 1 nm thick, with sensing properties determined by the detailed physical layer structuring of the device, and its constituent materials, at an atomic level - the crystalline structure is key to the functionality. However, the ever-increasing data storage density demanded for modern applications means that this technology is nearing its limit. Further improving this technology to accommodate data density beyond 1 Tb/sq-in requires smaller devices and lower device resistances, in order that the head may sense smaller data bits at a higher data throughput. Achieving both of these goals together necessitates reduction in the thickness of the insulating layer. As this layer is only a few atoms thick in state-of-the-art devices, this will soon no longer be possible; the rapid increase in digital data storage density demanded by technologically advanced society can no longer continue unless a new sensor technology is developed. A novel candidate technology has been suggested, based upon theoretical prediction of novel physics - quantum-coherent spin-dependent electron scattering resulting in the `quasimomentum-filtered giant magnetoresistance' (QF-GMR) effect. QF-GMR also depends intimately on the atomic scale structure of a hybrid device, now consisting of two magnetic layers, separated by a nanoscale non-magnetic spacer, and deposited onto an engineered semiconductor electrode; it is the logical next-generation spintronic device paradigm. Electrons emitted from the semiconductor have constrained lateral wavevector, or quasimomentum, due to the low semiconductor carrier density. This `filtered' quasimomentum results in strongly spin-selective transmission across the structure, producing orders-of-magnitude larger magnetoresistance. The absence of an insulating layer reduces the device resistance sufficiently for increasing data density; readback sensors based on QF-GMR should enable the continued increase in digital data storage density for years to come - 'more-Moore' improvement, continuing Moore's law. In addition to readback heads there are many areas of technology where devices based on QF-GMR may find application; potentially providing 'more-than-Moore' performance gains via novel functionality or architectures. Efficient microwave and spin-wave generation for 'magnonic' computing, spin-transfer torque diodes for sensitive radio-frequency current detection, and novel metallic devices based on quantum-well resonances are such potential applications. So-far no experimental demonstration of the predicted QF-GMR effect exists. This project primarily aims to provide such a demonstration, gain further understanding of the novel physics behind the QF-GMR, and advance sensor devices based on QF-GMR from theory toward future technological application. This research will demonstrate that QF-GMR devices may be a cost-effective solution to the problems in increasing data storage density which the hard disk industry will soon face, and also for future memory, radio-frequency and spin-wave communications and processing technologies based on quantum-wells and spin-transfer torque.
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