Final Year Projects 2021-2022 – You will be working on an individual project within a group focusing on magnetothermal effects. Below descriptions available for both part C an part D.
Developing a dynamic measurement of magnetothermal effects in thin films.
The 3 omega technique is an ac technique currently employed to measure the thermal conductivity of bulk and thin film samples. In this technique, a metallic heater strip is deposited onto the sample to be measured, where an alternating current at 1f is applied, thereby heating the sample at a frequency of 2f. The resulting temperature change in the heater strip results in an observable voltage at 3f. You will be exploring development of this for thermal conductivity measurements alongside exploring the potential of extracting indications of spin Seebeck (a magnetothermal) effect.
NiO thin films for antiferromagnetic spintronics
NiO is an antiferromagnetic insulator, which has been of interest in spintronics communities due to the ability to control the magnetic state by spin transfer torque. This has application in antiferromagnetic spintronics, which could be a new form of computing that transmits information by electron spin. It has also, recently been used as an intermediate thin film layer to enhance spin injection in multilayer devices (in particular for spin Seebeck effect). You will be measuring Heusler/NiO/Pt multilayers in particular the magnetoresistance and observed spin Seebeck effect.
Measurement of spin Seebeck devices
The spin Seebeck effect is a recently discovered phenomenon whereby a spin polarised current is generated in a magnetic material subjected to a temperature gradient. Detection of the spin polarisation current is achieved by placing a metal such as Pt in contact with the magnetic material so that the spin current is converted to a charge current by the inverse spin Hall effect. This project will be exploring measurement of spin Seebeck devices, where the aim is to convert waste heat into useful electrical power.
Use of harmonic Hall measurements in characterising spintronic devices
Spintronics – using the spin of an electron to convey information – requires knowledge on the efficiency of conversion of a spin current to a charge current (the spin Hall angle, θSH) by the spin Hall effect. A relatively simple way to determine this is to use ac Harmonic Hall measurements, where a Hall voltage is induced in response to an ac current. You will be developing this technique to measure potential spintronic devices.
Anomalous Hall effect in Co2MnSi (and other heusler materials)
The Anomalous Nernst Effect (ANE) in a magnetic material gives rise to an electric field (E) perpendicular to an applied temperature difference (ΔT), or heat flux (JQ), and magnetisation vector (M), (Figure 1). Recently a wide range of materials, from thin films to bulk single crystals, dilute magnetic semiconductors and topological insulators, have been shown to exhibit an enhanced ANE due to the topological properties of their band structures. You will be measuring the AHE of a series on Co2MnSi thin films, which have different levels of atomic disorder and comparing to changes in bandstructure determined separately by DFT.
