Biomedical Engineering Reference
In-Depth Information
16.2.2
Magnetic Properties
The magnetic properties (bulk) of the Co-based nanoparticles are usually charac-
terized using VSM or AGM. In AGM (see Figure 16.5a), the sample is mounted
on a piezoelectric transducer which oscillates when the sample is subjected to an
alternating magnetic fi eld gradient superimposed on the direct current (DC) fi eld
of an electromagnet. The force exerted on the magnetized sample in a magnetic
fi eld gradient can be measured. The AGM has a low noise fl oor of 10
− 8
emu, and
the piezoelectric reed sample holder of the magnetometer must be operated at the
resonance frequency of the sample holder, which depends on the mass of the
sample/substrate combination. Hence, every new sample requires re-tuning to its
Figure 16.5
Schematic diagrams of (a) an alternating gradient
magnetometer and (b) a vibrating sample magnetometer.
