<P> Single crystals of Zn2P207 containing 0.1% by weight of manganese impurity or 0.04% by weight of copper impurity were studied by means of electron spin resonance techniques from room temperature up to about 200°c. </p> <P> The existence of a phase transition at about 132°C in Zn2P2O7 was confirmed and a new phase, existing between 132°C and 155°C was found. The space group of the unit cell in this phase was deduced from the esr measurements. The spin Hamiltonian parameters were measured in the three phases and a discussion of their significance in terms of current theories of the zero field splitting of the ground state of S-state ionsis given. </p> / Thesis / Doctor of Philosophy (PhD)

Single crystals of (Mg₉₉.₇₅Mn₀.₂₅)₂P₂O₇ have been investigated by esr through the temperature range from room temperature to 200ºC. One phase transition was observed extended through the temperature range between 59.5ºC to 63ºC where the α-and β phase coexist. Accurate spectra were recorded at 74ºC, 84ºC and 94ºC at the three magnetic axis, and the spin-Hamiltonian parameters were obtained from these data. The phase transition mechanism and the significance of the spin-Hamiltonian parameters in the theory of S-state splitting are discussed in the light of current literature. / Thesis / Master of Science (MSc)