Elucidation Of The Cation And The Anion Doping Mechanism Of Nanoparticulate Manganese Arsenide: Effect Of Doping On The Magnetostructural Properties

ELUCIDATION OF THE CATION AND THE ANION DOPING MECHANISM OFNANOPARTICULATE MANGANESE ARSENIDE: EFFECT OF DOPING ON THEMAGNETOSTRUCTURAL PROPERTIESbyROSHINI PIMMACHCHARIGEMay 2017Advisor: Dr. Stephanie L. BrockMajor: ChemistryDegree: Doctor of PhilosophyThe evolution of MnAs nanoparticles in solution-phase synthesis and incorporation of Phas been quantitatively assessed and the knowledge obtained from adventitious doping isextended to independently control nanoparticle size and P incorporation in order to understandthe roles of size and dopant concentration on the magnetostructural properties. During thesolution-phase synthesis, the dimensions of the nanoparticles change simultaneously with themonomer concentration in the bulk solution and the particles become morphologically uniformwhen the temperature stabilizes. The temperature at which the nanoparticles were isolatedcontrols the particle size and polydispersity. High temperature isolation of nanoparticles isrequired to achieve narrow polydispersity and ultimately leads to a highly reproducible product.Adventitious phosphorus incorporation from the solvent TOPO occurs during nucleation, and Pis subsequently lost, likely due to self-purification. The reaction conditions for synthesis of nanoparticles of similar sizes with different Pconcentrations and different particle sizes with similar P concentrations were established and theeffect on magnetic and structural properties was evaluated. Temperature-dependent XRD studiesand magnetic measurements suggest that the transformation from β to α structure upon cooling is