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SUMMARY:Spin-Orbit Effects in Electron Transport (Prof. Bryan J. Hickey\, 
 University of Leeds) - Prof. Bryan J. Hickey\, School of Physics and Astro
 nomy\, University of Leeds
DTSTART:20140414T140000Z
DTEND:20140414T150000Z
UID:TALK50699@talks.cam.ac.uk
CONTACT:Dr. Jonathan D. Mar
DESCRIPTION:The spin-orbit interaction seems unavoidable in many aspects o
 f Condensed Matter Physics and in spintronics it is ubiquitous. Many of th
 e effects are understood and have been with us for a long time\, the aniso
 tropic magnetoresistance (AMR) of ferromagnets for example\, but recently\
 , it was proposed [1] that the AMR can exist in thin layers of Pt where on
 ly one atomic layer has an induced magnetisation by proximity. This is con
 troversial however\, as others think that the effect is actually the spin 
 Hall magnetoresistance. The interaction between electron spins and magnons
  in an insulating ferromagnet can give rise\, through the spin orbit inter
 action\, to a magnetoresistance that derives from the spin Hall and invers
 e spin Hall effects. We have studied this effect in platinum on Yttrium Ir
 on garnet (YIG) thin films. The YIG films have been made by RF magnetron s
 puttering grown on Gadolinium Gallium garnet substrates (GGG). We have use
 d these samples to measure the temperature dependence of the spin Hall mag
 netoresistance and fitted the data using a recently published theory [2]. 
 The spin-orbit interaction is evident in the origin of the effect and also
  in the temperature dependence through the Elliot-Yafet mechanism which we
  suggest is responsible for the spin relaxation.\n\nIn a very different sy
 stem we have been studying the spin-orbit effect that gives rise to quite 
 unexpected results. Lateral spin valves made from carbon nanotubes are int
 eresting candidates for spin dependent transport because they possess many
  of the desirable features of graphene and are already in a convenient sha
 pe for use as a conductor. Our lateral spin valves use single-wall nanotub
 es contacted by permalloy electrodes with a tunnel barrier between the met
 al and the nanotube. Thus the tube is a quantum dot and can be operated wi
 thin or outwith the Coulomb blockade (CB) regime. Outside the CB regime we
  measure a TMR of about 10% but more interestingly\, within the CB regime 
 where the device functions at the single electron level\, we measure magne
 toresistance in excess of 300%. Due to the sensitivity of the dot to its e
 nvironment\, the conductance of the dot can be changed electrostatically a
 nd the large MR is associated with tuning the dot on and off a CB resonanc
 e\, but without changing either the gate voltage or the source-drain bias.
  Using magnetic fields directed along the tube axis\, we have also demonst
 rated the full spin-orbit induced splitting of the dot energy levels and s
 how how these act as a spin filter for single electron transport.\n\n[1] L
 u\, Y.M.\, et al. Phys. Rev. Lett. 110\, 147207 (2013)\; [2] Chen\, Y.T.\,
  et al. Phys. Rev. B 87\, 144411 (2013).
LOCATION:Small Lecture Theatre\, Bragg Building\, Cavendish Laboratory (Ph
 ysics Department)
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