Measurement of the spin Seebeck effect
A relatively new phenomena – the spin Seebeck effect – manifests as the generation of a spin polarised current when a temperature difference is set up between two junctions of a magnetic material. This effect is of particular interest as it hints at the possibility of spin dependent thermal conductivities, a property that could lead to a breakthrough in energy harvesting technology. The measurement of this effect is possible by making use of the inverse spin Hall effect.
We have several sample holders designed to measure the spin Seebeck effect- from monitoring the temperature difference across a 10 mm wide sample, to large area (40 x 40 mm) sample holders with integrated Peltier cells to monitor the heat flux and temperature difference across the sample.
Measuring the Seebeck coefficient
The Seebeck effect manifests as a generation of a current (voltage) when a temperature difference occurs between two junctions. This can be used to harvest energy but in order to develop new materials a measure of the Seebeck coefficient (how much voltage is generated per Kelvin) is required.
Defining the First Order Phase Transition: Microcalorimetry
Using a commercial SiN gauge (TCG 3880) it is possible to measure separate contributions to the entropy change from heat capacity and latent heat. Sample sizes are typically of the order of micrograms and measurement sensitivity is of the order of nJ/K.
Transport measurements – 4 point probe
Utilising a Keithley 6221 current source and 2182 nanovoltmeter, Van der Pauw, Hall and Magneto-Resistance measurements are achievable with respect to magnetic field (~0-0.5 T) and temperature (~ 20-300 K). Capable of resistances ranging from mOhms to 20 MOhms.
Magnetic measurements – Magneto-Optic Kerr Effect
Using the change in polarisation of light interacting with magnetic material (Kerr effect) to determmine the coercive field of thin films. Capable of magnetic field +/-0.1T.
Also available in department:
– X Ray Diffraction and Reflectivity
– Differential Scanning Calorimetry
– Thermal conductivity measurements
– Sample preparation and characterisation (e.g. arc furnace, PLD, PVD, metallurgical microscope with camera)