In this thesis we investigate various aspects of SAW devices and strain sensitive spin species in ZnO and LiNbO<sub>3</sub> for coupling surface acoustic waves to spin ensembles. Firstly, we performed a series of ESR experiments exploring the potential of Fe<sup>3+</sup> impurities in ZnO for spin-lattice coupling. This spin system has already been identified as a high potential quantum technology component due to its long coherence time. We show that the system also has good properties for spin-lattice coupling experiments, with a strain-coupling parameter G<sub>33</sub> = 280 ± 5GHz/strain, which is about 16 times larger than the largest reported for NV centres in diamond. We found that the LEFE effect as well as the spin Hamiltonian parameter D have a linear temperature dependence. As the relative change in each coincide, this strongly supports the notion that the modification of D by an electric field is a multiplicative effect rather than an additive one, D = D<sub>0</sub>(1 + κΕ). The LEFE coefficient we measured is several times larger for Fe<sup>3+</sup>:ZnO than for Mn<sup>2+</sup>:ZnO. Secondly, we have fabricated and characterised SAW devices on bulk ZnO crystals and Fe doped lithium niobate. We found that the nominally pure ZnO was conductive at room temperature due to n-type intrinsic doping, and electrical losses inhibited any transmission through a SAW delay line above T = 200K. The one-port resonator measured down to milli-Kelvin temperatures showed excellent quality factors of up to Q ≃ 1.5 x 10<sup>5</sup> in its superconducting state. Finally, we performed a surface acoustic wave spin resonance (SAWSR) experiment using a one-port SAW resonator fabricated on Fe<sup>2+</sup>:LN. We observed a clear signal at T ≃ 25 K, at a field near the expected one for a Δm<sub>s</sub> = 2 transition between the |â1⟩ and |+1⟩ states. We concluded it to be a transition induced by acoustic coupling since the signal intensity did not tend to zero when the magnetic field was parallel to the crystal anisotropy axis. Furthermore, this tells us that the coupling is due to a modulation of the E zero-field splitting parameter rather than D. We investigated the dependence on microwave power and found the saturation limit. We performed a measurement of Fe<sup>3+</sup>:LN as well to reassure ourselves that the resonance is not magnetically excited by the field around the IDT.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:730391 |
| Date | January 2016 |
| Creators | Magnusson, Einar B. |
| Contributors | Ardavan, Arzhang ; Leek, Peter J. |
| Publisher | University of Oxford |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | https://ora.ox.ac.uk/objects/uuid:09d23fb2-f501-4be2-a25f-b69ada0ce5b1 |
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