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Temperature-dependent structure of Tb-doped magnetite nanoparticles



Katherine P. Rice, Stephen E. Russek, Roy H. Geiss, Justin Shaw, Robert J. Usselman, Eric R. Evarts, Thomas J. Silva, Hans Nembach, Elke Arenholz, Yves U. Idzerda


High quality 5 nm cubic Tb-doped magnetite nanoparticles have been synthesized by a modified wet-chemical method to investigate tailoring of magnetic properties for imaging and biomedical applications. We show that the Tb is incorporated into the octahedral 3+ sites. High angle annular dark field microscopy shows that the dopant is well-distributed throughout the particle and x-ray diffraction measurements show a small lattice parameter shift with the inclusion of a rare-earth dopant. Magnetization and x-ray magnetic circular dichroism data indicate that the Tb spins are unpolarized and weakly coupled to the iron spin lattice at room temperature, and begin to polarize and couple to the iron oxide lattice at temperatures below 50 K. Broadband ferromagnetic resonance measurements show no increase in magnetic damping at room temperature for Tb-doped nanoparticles relative to undoped nanoparticles, further confirming small coupling between iron and Tb spins at room temperature. The Gilbert damping constant α is remarkably low for the Tb-doped nanoparticles with α = 0.024 ± 0.003. These nanoparticles, which have a large fixed moment, a large fluctuating moment and optically active rare-earth elements, are potential high- relaxivity T1 and T2 MRI agents with integrated optical signatures.
Applied Physics Letters


nanoparticles, ferromagnetic resonance, x-ray magnetic circular dichroism, rare-earth dopants


Rice, K. , Russek, S. , Geiss, R. , Shaw, J. , Usselman, R. , Evarts, E. , Silva, T. , Nembach, H. , Arenholz, E. and Idzerda, Y. (2015), Temperature-dependent structure of Tb-doped magnetite nanoparticles, Applied Physics Letters, [online],, (Accessed June 13, 2024)


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Created February 12, 2015, Updated October 12, 2021