Investigation of rare-earth pyrochlore thin films

This thesis reports on a number of systematic studies that were carried out on thin films of spin ice and its related materials. Specifically, three series were carried out: a thickness series and an epitaxial strain series reporting on Yb₂Ti₂O₇ thin films; a series investigating the thickness-dependence of Tb₂Ti₂O₇ films' specific heat; and lastly, a characterisation of thick Dy₂Ti₂O₇, Tb₂Ti₂O₇ and Yb₂Ti₂O₇ films. The epitaxial strain series of Yb₂Ti₂O₇ showed that fully strained films of Yb₂Ti₂O₇ could be grown on Y₂Ti₂O₇ substrates with an out-of-plane crystal direction of [1¯10] and [100]. The thickness series was carried out on films with an out-of-plane crystal direction of [111], but it is shown that this particular orientation is more challenging to grow fully strained films along because in all instances the films were relaxed. The aim of the Tb₂Ti₂O₇ series was to investigate the nature of the films' ground states, which have been subject to debate in the bulk. Single-ion model fittings imply that the ground state of the Tb₂Ti₂O₇ thin films is a doublet state. The thick film series shows that a fully strained Dy₂Ti₂O₇ film was grown, but that the other films created additional phases and, in the case of Tb₂Ti₂O₇, did also relax. Specific heat measurements reveal that the thick Dy₂Ti₂O₇ film has recovered some but not all of its residual entropy, which is seen in the bulk. This means that the phase grown is both different to the previous thin films grown and to the bulk. Fits to M vs H measurements give a magnetic moment of 9.4(1) μB, which is within error of the bulk