Abstract
The magnetic susceptibility (κRT) and saturation magnetization (MS) of microbially synthesized magnetites were systematically examined. Transition metal (Cr, Mn, Co, Ni and Zn)- and lanthanide (Nd, Gd, Tb, Ho and Er)-substituted magnetites were microbially synthesized by the incubation of transition metal (TM)- and lanthanide (L)-mixed magnetite precursors with either thermophilic (TOR-39) or psychrotolerant (PV-4) metal-reducing bacteria (MRB). Zinc incorporated congruently into both the precursor and substituted magnetite, while Ni and Er predominantly did not. Microbially synthesized Mn- and Zn-substituted magnetites had higher κRT than pure biomagnetite depending on bacterial species and they exhibited a maximum κRT at 0.2 cationic mole fraction (CMF). Other TMs' substitution linearly decreased the κRT with increasing substitution amount. Based on the MS values of TM- and L-substituted magnetite at 0.1 and 0.02 CMF, respectively, Zn (90.7 emu/g for TOR-39 and 93.2 emu/g for PV-4)- and Mn (88.3 emu/g by PV-4)-substituted magnetite exhibited higher MS than standard chemical magnetite (84.7 emu/g) or pure biomagnetite without metal substitution (76.6 emu/g for TOR-39 and 80.3 emu/g for PV-4). Lanthanides tended to decrease MS, with Gd- and Ho-substituted magnetites having the highest magnetization. The higher magnetization of microbially synthesized TM-substituted magnetites by the psychrotroph, PV-4 may be explained by the magnetite formation taking place at low temperatures slowing mechanics, which may alter the magnetic properties compared to the thermophile, through suppression of the random distribution of substituted cations.
Original language | English |
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Pages (from-to) | 283-292 |
Number of pages | 10 |
Journal | Journal of Magnetism and Magnetic Materials |
Volume | 313 |
Issue number | 2 |
DOIs | |
State | Published - Jun 2007 |
Funding
The authors thank Les Beard, UT-Battelle for help measuring magnetic susceptibility and the Shared Research Equipment (SHaRE) User Facility in the Material Science and Technology Division, Oak Ridge National Laboratory (ORNL) for assistance with XRD analyses. J.-W. Moon is supported by an appointment to the ORNL Postdoctoral Research Associates Program administered jointly by the Oak Ridge Institute for Science and Education and ORNL. This research was supported by the Defense Advanced Research Projects Agency (DARPA) Biomagnetics Program under Contract 1868-HH43-X1 and the US Department of Energy's (DOE) Office of Fossil Energy with student support provided by the DOE Environmental Molecular Science Initiative. ORNL is managed by UT-Battelle, LLC, for the US DOE under Contract DE-AC05-00OR22725.
Keywords
- Lanthanide
- Magnetism
- Magnetite
- Microbial synthesis
- Transition metal