Size- and composition-dependent radio frequency magnetic permeability of iron oxide nanocrystals.
We investigate the size- and composition-dependent ac magnetic permeability of superparamagnetic iron oxide nanocrystals for radio frequency (RF) applications. The nanocrystals are obtained through high-temperature decomposition synthesis, and their stoichiometry is determined by Mössbauer spectroscopy. Two sets of oxides are studied: (a) as-synthesized magnetite-rich and (b) aged maghemite nanocrystals. All nanocrystalline samples are confirmed to be in the superparamagnetic state at room temperature by SQUID magnetometry. Through the one-turn inductor method, the ac magnetic properties of the nanocrystalline oxides are characterized. In magnetite-rich iron oxide nanocrystals, size-dependent magnetic permeability is not observed, while maghemite iron oxide nanocrystals show clear size dependence. The inductance, resistance, and quality factor of hand-wound inductors with a superparamagnetic composite core are measured. The superparamagnetic nanocrystals are successfully embedded into hand-wound inductors to function as inductor cores.
Department of Chemistry, ‡Department of Materials Science and Engineering, §Department of Electrical and Systems Engineering, and ⊥Department of Physics and Astronomy, University of Pennsylvania , Philadelphia, Pennsylvania 19104, United States.
Hongseok
H
Yun
Xiyu
X
Liu
Taejong
T
Paik
Duraivelan
D
Palanisamy
Jungkwun
J
Kim
William D
WD
Vogel
Arthur J
AJ
Viescas
Jun
J
Chen
Georgia C
GC
Papaefthymiou
James M
JM
Kikkawa
Mark G
MG
Allen
Christopher B
CB
Murray
inductor; maghemite; magnetic susceptibility; magnetite; radio frequency; superparamagnetism