Esteban Perez

Major: Electrical Engineering
Mentors: Steven Gomez, Professor Stephen Wilson

Synthesis of the Pyrochlore Pr2GaSbO7 using a Hybrid Mechanochemical/Microwave-Assisted Method 

To realize robust quantum computers, we must better understand how exotic quantum states behave in electronic and magnetic materials. Frustrated magnetism is a phenomenon that arises when the geometry of atomic bonds inside a solid does not allow the spins of unpaired elec- trons to find equilibrium, and this frustration can lead to exotic mag- netic behavior. In the family of Pr-based pyrochlore oxide compounds (Pr2B2O7), one such exotic state is the so-called “spin ice” state, whose physics may be tuned via the distance between Pr3+ ions. However, the size of the Pr3+ ion places this family of compounds close to the limit of the pyrochlore phase stability window, making the pyrochlore structure unstable for B-site cations smaller than Sn (i.e., Ti). Here we show that by using a novel microwave synthesis technique it is pos- sible to synthesize Pr2GaSbO7, whose mixed B-site places the Pr3+ ions closer than in any other compound in the family. We show that the synthesis is limited by persistent impurities such as Pr3SbO7 and a langasite-related compound of unknown composition. The quantity of impurities is highly dependent on gas environment, heating profile, and stoichiometry, suggesting that Pr2GaSbO7 lies not only on the edge of the structural stability window, but also competes with other thermo- dynamically favorable phases. A phase purity of ∼ 90% by mass was achieved using a moderate heating profile and by improving homogene- ity and density of the sample before reaction. Our results demonstrate that realizing a phase-pure sample of Pr2GaSbO7 may be possible, and the key may lie in sample stoichiometry and homogeneity/density of the powder before heating. We anticipate that studying the physics of Pr2GaSbO7 will help to elucidate how the distance between Pr3+ ions affects the exotic fluctuations present in other Pr-based pyrochlores will the enhanced interactions destroy the exotic fluctuations, or will they persist?