J. Wittborn et al., Magnetization reversal observation and manipulation of chains of nanoscalemagnetic particles using the magnetic force microscope, NANOSTR MAT, 12(5-8), 1999, pp. 1149-1152
The magnetization reversal of chains of 40-50 nanometer, magnetic particles
has been studied using Magnetic Force Microscopy (MFM) in an applied field
. The field was stepwise increased and decreased in order to make hysteresi
s loops for the chains. The magnetic particles magnetosomes biomineralized
by magnetotactic bacteria, are single crystal Fe3O4 with a narrow size dist
ribution. A method for extracting Switching Field Distributions (SFD 's) fr
om sets of MFM images of such chains was developed The coercivity was found
to increase with the number of particles in a chain up to 7 or 8 particles
and then decrease with increasing number of magnetosomes. After the initia
l reversal observations one of the chains was cut into smaller pieces using
the MFM-tip, thus producing separated chain segments, which resulted in al
tered inter-particle interactions. Additionally, multiple hysteresis loops
were made for the same chain, showing that the field from the tip affects t
he sample magnetization. (C) 1999 Acta Metallurgica Inc.