178 8 Magnetic Nanomaterials, Superparamagnetism
reduce eddycurrent losses, often the particles are coated with an insulating layer.
In most cases, however, these materials are produced by annealing of metallic
glassy ribbons. In this context alloys with compositions based on FeSiBNbCu or
FeZrB are under discussion. As the constant of magnetic anisotropy of these
materials is well below 10
3 J m
−3 , the correlation volume is of macroscopic size.
These materials have been commercialized for many years, the same is valid, for
example, for composites consisting of metallic particles coated with silica.
Figure 8.31 Specific loss power of ferrite
nanoparticles. These are uncoated and
ferrite-coated particles. Due to different
particle sizes, an exact interpretation of the
results is difficult; however, one can conclude
that the coated, exchange-coupled particles
show higher losses [9]. (At the coated
particles, the first mentioned compound is
the core, the second one the coating.)
0
500 1000 1500 2000 2500 3000 3500
specific loss power [J s
–1
g
–1
]
Fe3O4
CoFe3O4
MnFe2O4
CoFe2O4/Fe3O4
Fe3O4/CoFe2O3
CoFe2O4/MnO2
MnFe2O4/CoFe2O4
CoFe 2 O 3
MnFe 2 O 3
CoFe 2 O 3 /Fe 3 O 4
Fe 3 O 4 /CoFe 2 O 3
CoFe 2 O 3 /MnFe 2 O 3
MnFe 2 O 3 /CoFe 2 O 3
Fe 3 O 4
References
1 Néel, L. (1949) C. R. Acad. Sci. Paris, 228,
664–666.
2 Aharoni, A. (1964) Phys. Rev. A, 132,
447–440.
3 Morup, S., and Christiansen, G. (1993)
J. Appl. Phys., 73, 6955–6957.
4 Tang, Z.X., Sorensen, C.M., Klabunde,
K.J., and Hadjipanayis, G.C. (1991) Phys.
Rev. Lett., 67, 3602–3605.
5 Kodama, R.H., Berkowitz, A.E., McNiff,
E.J., and Foner, S. (1997) J. Appl. Phys.,
81, 5552–5557.
6 Vollath, D., and Szabó, D.V. (2002)
Innovative Processing of Films and
Nanocrystalline Powders (ed. K.L. Choy),
Imperial College Press, London,
pp. 219–251.
7 Han, D.H., Wang, J.P., and Luo, H.L.
(1994) J. Magn. Magn. Mater., 136,
176–182.
8 Vollath, D., Szabó, D.V., and Willis, J.O.
(1996) Mater. Lett., 29, 271–279.
9 Lee, J.H., Jang, J.T., Choi, J.S.,
Moon, S.H., Noh, S., Kim, J., Kim,
reduce eddycurrent losses, often the particles are coated with an insulating layer.
In most cases, however, these materials are produced by annealing of metallic
glassy ribbons. In this context alloys with compositions based on FeSiBNbCu or
FeZrB are under discussion. As the constant of magnetic anisotropy of these
materials is well below 10
3 J m
−3 , the correlation volume is of macroscopic size.
These materials have been commercialized for many years, the same is valid, for
example, for composites consisting of metallic particles coated with silica.
Figure 8.31 Specific loss power of ferrite
nanoparticles. These are uncoated and
ferrite-coated particles. Due to different
particle sizes, an exact interpretation of the
results is difficult; however, one can conclude
that the coated, exchange-coupled particles
show higher losses [9]. (At the coated
particles, the first mentioned compound is
the core, the second one the coating.)
0
500 1000 1500 2000 2500 3000 3500
specific loss power [J s
–1
g
–1
]
Fe3O4
CoFe3O4
MnFe2O4
CoFe2O4/Fe3O4
Fe3O4/CoFe2O3
CoFe2O4/MnO2
MnFe2O4/CoFe2O4
CoFe 2 O 3
MnFe 2 O 3
CoFe 2 O 3 /Fe 3 O 4
Fe 3 O 4 /CoFe 2 O 3
CoFe 2 O 3 /MnFe 2 O 3
MnFe 2 O 3 /CoFe 2 O 3
Fe 3 O 4
References
1 Néel, L. (1949) C. R. Acad. Sci. Paris, 228,
664–666.
2 Aharoni, A. (1964) Phys. Rev. A, 132,
447–440.
3 Morup, S., and Christiansen, G. (1993)
J. Appl. Phys., 73, 6955–6957.
4 Tang, Z.X., Sorensen, C.M., Klabunde,
K.J., and Hadjipanayis, G.C. (1991) Phys.
Rev. Lett., 67, 3602–3605.
5 Kodama, R.H., Berkowitz, A.E., McNiff,
E.J., and Foner, S. (1997) J. Appl. Phys.,
81, 5552–5557.
6 Vollath, D., and Szabó, D.V. (2002)
Innovative Processing of Films and
Nanocrystalline Powders (ed. K.L. Choy),
Imperial College Press, London,
pp. 219–251.
7 Han, D.H., Wang, J.P., and Luo, H.L.
(1994) J. Magn. Magn. Mater., 136,
176–182.
8 Vollath, D., Szabó, D.V., and Willis, J.O.
(1996) Mater. Lett., 29, 271–279.
9 Lee, J.H., Jang, J.T., Choi, J.S.,
Moon, S.H., Noh, S., Kim, J., Kim,