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The Spintronics group has expertise in both microwave and optical excitation techniques, magnetic resonance, device fabrication, and low-temperature measurements
Our lab is equipped to perform a wide range of measurements combining several areas of spintronics research.
Recent projects:
- Spin-orbit torques: The spin-orbit interaction for controlling various spin states
The coupling of spin and motion mediated by the spin-orbit interaction can provide a bi-lateral access of these two quantities - spin & motion (or transport), of electrons. As a result, the spin-orbit interaction can empower us to control electron spins through electric excitations - it seems we have better controllabilities of charge than spin as history explains. Electrons in a crystal with broken inversion symmetry experience different energy levels determined by the directions of both motion and spin. Controlling the motional component (by applying a current through), we can therefore access to the electron spin population. This is a current-induced spin polarisation and if one does this in ferromagnetic materials, you can also control the localised electron spins that is hardly susceptible to applying a current - that's why they are called "localised". We are in part of an active international research collaboration (with many world-leading researchers in the world), and attempt to understand the microscopic pictures of current-induced spin polarisation and mangetisation control, in as view of harnessing for technology. Some details of this would be found in the following papers.
Related papers:
"An anti-damping spin-orbit torque originating from the Berry curvature", Nature Nanotechnology 9 211 (2014)
“Spin-orbit-driven ferromagnetic resonance”, Nature Nanotechnology 6 413 (2011).- Spin Hall phenomena
The spin-Hall effect is another branch of the spin-orbit phenomena, and using it is an alternative route for spin generation (and detection) pursuits. There is soon to be an interesting paper coming up from our research team, on which we provide an unusual way of controlling the spin-Hall effect. We will build on this study as well as examine several different research hypotheses to more understand and exploit the spin-Hall effect. Again, this project and ourselves benefit from its strong nature of international collaborations.
Related papers:
"Electric control of the spin-Hall effect by inter-valley transitions" Nature Mater. 13 932 (2014)
"Polaron Spin Current Transport in Organic Semiconductors" Nature Phys. 10 308 (2014)
“Electrically tunable spin injector free from the impedance mismatch problem” Nature Mater. 10 655 (2011).- Non-linear Magnetic Dynamics
Non-linear magnetic dynamics for fundamental spin physics and spintronic applications
In collaboration with Prof Demokritov's group, Germany, we work on fundamental physics about how (spin) angular momentum behave within spin-waves and other outer environments such as electrons and the lattice. Nonlinear magnetic dynamics is our particular focus, which sometimes offers very peculiar physics that often looks counter-intuitive but does not violate some fundamental thermodynamics rules. Our finding of spin current amplification using three-magnon splitting is just an example - learn more from the following links for this direction.
Related papers:
- “Controlled enhancement of spin current emission by three-magnon splitting”, Nature Mater. 10 660 (2011).
- "Uniaxial anisotropy of two-magnon scattering in an ultrathin epitaxial Fe layer on GaAs" Appl. Phys. Lett. 102 082415 (2013).
- “Spin pumping by parametrically excited short-wavelength spin waves” Appl. Phys. Lett. 99 162502 (2011).
Book chapter:
- Control of Pure Spin Current by Magnon Tunneling and Three-Magnon Splitting in Insulating Yttrium Iron Garnet Films, ch. 4, Recent Advances in Magnetic Insulators - From Spintronics to Microwave Applications
- Friday Afternoon Projects
My research ethos - I love people to just follow their thoughts of "it's cool to do this and that". I will secure some of my lab spaces dedicated to this, for more less fun-loving side of research that (at least) delocalises ourselves from productivity-oriented research that we normally do, or have to. There are a few ongoing projects like this, waiting to find themselves materialised into some forms. Let me know if you want to join us!
- Dr Kurebayashi
Equipment:
Cleanroom
As part of the London Centre for Nanotechnology (LCN), the SPiN group has access to world-class micro-fabrication facilities. For more information about the LCN Cleanroom and a list of available equipment, please see the cleanroom website.
Optical Spin Excitations
Our optical equipment focuses a laser beam onto semiconductor samples. A photo-elastic modulator is used to provide the beam with an alternating circular polarisation, which induces an alternating spin-population in the sample. Our objective lens is mounted on a stepper-motor controlled 3-axis stage to control positioning and focusing of the laser spot. A beam splitter and CMOS camera allow us simultaneously to image the sample. We study the effects of the spin-polarisation on the electric and magnetic transport properties of the samples.
Variable Temperature Ferromagnetic Resonance
Our home-built setup consists of a GMW 3473 rotating magnet combined with a modified Oxford Instruments ACV12 closed cycle cryostat. We have wired microwave and dc lines into the cryostat to perform on-chip FMR and magneto-transport measurements. An interchangeable set of cold fingers allow us to mount our samples horizontally and vertically in the magnetic field. Magnetic fields > 1T and temperatures down to 2K can be reached.
Funding:
