Colloquium: Dr. Thelma BerquoDepartment of Physics Concordia College Moorhead, MN
Magnetic Interactions of Antiferromagnetic Nanoparticles: Investigation of Synthetic and Biological Ferrihydrite
I will report on the investigation of magnetic interactions of the antiferromagnetic iron oxide ferrihydrite by comparing magnetic properties of uncoated and coated particles. Four different coating agents (sugar, alginate, lactate and ascorbate) were employed to prepare sub-samples from the same batch of synthetic ferrihydrite, and magnetic and non-magnetic techniques were used to characterize the samples. We show that when a coating agent is added a dramatic drop in blocking temperature as well as the existence of exchange bias in hysteresis loops (FC-cooled) occur. Mössbauer spectra patterns for coated and uncoated particles are also distinctive. We found out that particle coating has an important contribution on the magnetic properties ferrihydrite. In addition, we show how the results obtained from synthetic ferrihydrite can help us to better understand the magnetic properties of Fe microbial mat deposited on hydrothermal vents at Loihi Seamount (Hawaii).