Subcategory: Materials Science
Frederick A. Pearsall - The City College of New York
Co-Author(s): Stephen O'Brien. The City College of New York, NY
Discovery of new complex oxides that exhibit coupled ferromagnetic and ferroelectric properties is of great interest for the design of functional magnetoelectrics, in which research is driven by the long-term technological prospect of controlling ferromagnetic hysteresis with an electric field and vice versa. Multiferroics offer opportunities for sensors, 4-state logic (NVM), and spintronics. Single-phase coupled multiferroics are of theoretical interest due to the possibility of a quantum character in such coupling. BaMn3Ti4O14.25 (BMT-134) is a recently discovered single-phase multiferroic complex oxide exhibiting antiferromagnetic and ferroelectric behavior. In an attempt to exhort a room temperature ferroic order response, BMT-134 was doped with Fe at varying degrees. Using a chemical solution processing approach, three distinct variations of nanocrystals were synthesized; BaMn3-xFexTi4O14.25 (BMFT) with x = 0.75, x = 1, x = 1.5, x = 2, x = 2.25. All variants were found to belong to the same hollandite crystal class as BMT-134 and Fe was shown to be incorporated into the crystals of each, with high product to precursor ratio fidelity. Using EDS, elemental composition was determined qualitatively and iron content was corroborated with precursor amount. Mossbauer spectroscopy was used to determine the oxidation state of Fe and to probe its chemical environment. TEM and SEM techniques were used to determine size distribution and morphology of the nanoparticles and of their packing within pellets. The effective permittivity of pellet pressed capacitors was measured for each Fe variant to probe the energy storage dependence on Fe content. M-T and M-H measurements were done using a SQUID magnetometer in order to determine how increasing Fe content changes the magnetic properties of the parent system. Such measurements show a trend when comparing iron content and magnetization. It has been experimentally shown that adding iron destroys the antiferromagnetic properties of the parent system. Instead, the iron variants are paramagnetic, unable to retain a magnetization even at low temperatures. Future work will focus on determining whether iron affects the ferroelectric properties of the parent system. Nanocrystals have been generally shown to lose bulk properties, including ferromagnetism and ferroelectricity; experiments in the future will determine whether or not these magnetic and electronic responses are size-dependent.ERNtitle_abstract_FredPearsall.docx
Funder Acknowledgement(s): 1. CREST : 2. AGEP
Faculty Advisor: Stephen O'Brien, email@example.com
Role: I have done all of the research myself.