Biomedical Engineering Reference
In-Depth Information
Table 15.2
Dynamic mode MFM studies in ambient air performed on magnetic nanomaterials.
Sample type
Sample dimensions
Reference
Ferromagnetics
Permalloy dots
1 mm diameter with 50 nm thickness
[57]
L a
0.7
Sr
0.3
MnO
3
(LSMO)
grown on SrTiO
3
surfaces
500 nm diameter patterned islands
[58]
γ
- Fe
2
O
3
particles
Prolate ellipsoids, 300 nm
×
65 nm
[59]
Co dots
[60]
140
×
250 nm laterally with 7 nm thickness
Fe dots
40 - 120 nm in diameter, with 40 nm
thickness
[61]
α
- MnAs quantum dots
Single - domain ferromagnets
∼
50 nm in
[62]
diameter
ε
- Co
12 nm particles
[63]
Superparamagnetic/
biological MNPs
MNPs from bacteria
Chain of 10 particles, each 70 nm in size
[64]
Magnetostatic bacteria
17.5 nm in diameter with 50 nm thickness
[46]
EPR spin probe
[28]
Prolate ellipsoids, 1
μ
m
×
100 nm
Iron oxide particles
10 nm iron - oxide cores, surrounded by
dextran matrix
[2]
EPR = electron paramagnetic resonance.
15.9.1
Ferromagnetic Nanoparticles
MFM has been used to study the domain structure of 500 nm islands of
La
0.7
Sr
0.3
MnO
3
(LSMO) grown on SrTiO
3
surfaces [58]. For structures with in-plane
magnetization, these stray fi elds emanate from the domain walls, instead of the
domains themselves. MFM images demonstrate that, for LSMO islands on
(110)- oriented SrTiO
3
substrates, the domain pattern varies depending on the
shape of the island (Figure 15.5A). Calculations based on the magnetostatic energy,
the anisotropy energy, and the domain wall energy, support these fi ndings and
predict that for diameters
>
50 nm the fl ux closure or vortex domain is the energeti-
