Design and optimisation of a novel magnetic detection scheme for encoded magnetic information carriers.

Previous work in the field has outlined a method to create micron-sized, tuneable encoded magnetic information carriers that can be redeposited through a liquid suspension. This thesis aims to build on this work, further characterising the information carriers and presenting a possible novel detection technique. The magnetic information carriers in this work use synthetic antiferromagnetic (SAF) particles with perpendicular magnetic anisotropy (PMA), attenuating the coupling strength between the magnetic layers using a platinum interlayer. This provides a controllable magnetic parameter which is used as the basis for the magnetic encoding. These particles can be lifted off the substrate into a solution for redeposition onto a surface which provides a magnetic ‘tag’. The particles are presented and characterised, including statistical distributions of switching events to better understand their detectable properties. A novel detection scheme for these particles is then proposed using inductive sensing and a rotating permanent magnet as a drive field source. Device efficacy is evaluated using computational simulations, allowing for the optimisation of the parameter space before physical building. The efficacy of different input parameters is evaluated using a figure of merit – the number of possible channels the detector can measure. The simulations begin with an idealised model of the detector and particle set, with zero coercivity SAF particles and perfect alignment. The different methods that the detector can be used in are assessed, as well as exploring the possible input geometries. Real-world constraints are later built into the model including the switching distributions of particles and the effects of misalignment. From these, the build constraints and electronic requirements of the system can be characterised. The detector is finally presented virtually through computer-aided design, which would be used to create a prototype model of the device

Object Composition Identification by Measurement of Local Radio Frequency Magnetic Fields with an Atomic Magnetometer

Proof of principle of object composition identification based on inductive measurements with an atomic magnetometer has been demonstrated in highly engineered laboratory conditions. Progress in the development of portable miniaturised magnetometers has encouraged on the parallel development of the measurement technologies involving this sensor, in particular concepts that would enable operation in complex test scenarios. Here, we explore the problem of material identification in the context of measurements performed with variable distance between the object and the primary radio-frequency field source and sensor. We identify various aspects of the measurement affected by variable distance and discuss possible solutions, based on the signal phase analysis, a combination of frequency and angular signal dependencies and the implementation of a pair of excitation coils

Object Composition Identification by Measurement of Local Radio Frequency Magnetic Fields with an Atomic Magnetometer

Proof of principle of object composition identification based on inductive measurements with an atomic magnetometer has been demonstrated in highly engineered laboratory conditions. Progress in the development of portable miniaturised magnetometers has encouraged on the parallel development of the measurement technologies involving this sensor, in particular concepts that would enable operation in complex test scenarios. Here, we explore the problem of material identification in the context of measurements performed with variable distance between the object and the primary radio-frequency field source and sensor. We identify various aspects of the measurement affected by variable distance and discuss possible solutions, based on the signal phase analysis, a combination of frequency and angular signal dependencies and the implementation of a pair of excitation coils

Demonstration of polycrystalline thin film coatings on glass for spin Seebeck energy harvesting - dataset

<div>Zip file with all raw XRD, XRR, transport data.</div>Origin project(s) containing raw and processed data for related publication.<div><br></div><div>Figure 1 was schematic only and not included here.</div><div>Figure 2 and Figure S2 are in the same origin project (simple and extended TEM data).</div><div><br></div><div>Figure captions:</div><div><p></p><p>Figure 2 TEM analysis of SSE5a. a) & b) STEM/BF and HAADF images of the thin film, respectively. c) Conventional HREM of the PM Pt layer. d) EDX line-scan performed perpendicular to the interfaces of the layers.</p><p></p><p>Figure 3 Summary of the magnetic, electric and thermal properties. a) Spin Seebeck voltage, <i>V_ISHE</i> (symbols), as a function of applied magnetic field plotted alongside magnetic data (line). b) Resistivity of the devices as a function of <i>t_PM</i>. c) Normalised spin Seebeck voltage, <i>S_SSE</i>, as a function of <i>t_PM</i>, plotted alongside simulated <i>S_SSE</i> (<i>θ_SH</i> = 0.1, <i>λ_SD</i> = 2 nm, <i>M_s</i> = 90 Am²/kg, D = 71x10⁴¹ Jm²[19], <i>g_r</i> = 1,3 & 5x10¹⁸ m^-2[20]). d) Definition of the parameters used to describe heat flow, (e) & (f) Change in <i>ΔT₂</i>, and <i>S_SSE</i> with substrate's thermal conductivity, <i>κ₃</i>.</p><p>Figure S1 Characterisation of the Fe₃O₄ film. a) SQUID magnetometry above and below the Verwey transition, <i>T_V</i>. b) Resistivity as a function of temperature. c) XRD of a set of 4 separately prepared Fe₃O₄ films. The inset shows a close-up of the (311), (222) peaks. d) Example XRR data (symbols) and fit (solid line), indicating thickness = 79 nm, roughness = 1.5 nm.</p><p></p><p>Figure S2 TEM analysis of SSE5a. a) & b) STEM/BF and HAADF images of the thin film, respectively. c) Conventional HREM of the PM Pt layer. d) & e) STEM/BF image of the thin film stack and corresponding EDX line-scan performed perpendicular to the interfaces of the layers, respectively, and f) schematic of the grain growth described in the text.</p><p></p><p>Figure S3 Characteristics of the bilayer film. a) XRD of SSE5a (2.5 nm Pt) and SSE20a (7.3 nm Pt). Inset shows a close-up of the Pt peak. b)  XRR fit of SSE5a; Pt thickness = 2.5 nm, roughness = 2 nm.</p><p></p><p>Figure S4 Example spin Seebeck measurement for SSE7a (<i>t_PM</i> = 3.2 nm) measured in fixed field as a function of temperature difference. Note that the sign convention for measurements, defined in Fig 1(a) of the main manuscript follows from Uchida <i>et al.</i>[6].</p></div