34
Ò. Iglesias and H. Kachkachi
compare with experiments. It has thus been possible to figure out how the magnetization of the nanomagnet switches, to evaluate the corresponding relaxation time and
the switching magnetic field. The macroscopic models such as the Stoner-Wohlfarth
and Néel-Brown models have already been validated by experiments performed on
nanomagnets for which these models are applicable. In the opposite situation induced
by surface effects, we may say that only qualitative studies have been relatively successful, whereas any quantitative investigation still remains a challenge. However,
the fast progress in synthesis, characterization and measurement has allowed for an
unprecedented control of a whole set of properties of these nanomagnets and has
made it to possible to shrink the gap between theory and experiments. In particular,
the possibility of making well organised, nearly monodisperse assemblies of well
defined nanomagnets, offers a real potential for studying the competition between,
on one hand the intrinsic properties due to finite-size and boundary, shape and surface effects, and on the other the collective effects induced by mutual interactions
between the nanomagnets and by their interactions with the hosting medium. This
relatively favorable situation has triggered new impetus for further investigations of
NMs assemblies with a plethora of promising practical applications.
Acknowledgements Ò.I. acknowledges financial support form the Spanish MINECO (No. MAT201568772 and No. PGC2018-097789-B-I00), Catalan DURSI (No. 2017SGR0598) and European
Union FEDER Funds (una manera de hacer Europa), also CSUC for supercomputer facilities.
References
1. D.S. Schmool, H. Kachkachi, in Single-Particle Phenomena in Magnetic Nanostructures
(Chap. 4), Solid State Physics, vol. 66, ed. by R.E. Camley, R.L. Stamps (Academic Press,
2015), pp. 301 – 423. https://doi.org/10.1016/bs.ssp.2015.06.001. http://www.sciencedirect.
com/science/article/pii/S0081194715000053
2. H. Kachkachi, D.A. Garanin, Physica A 300, 487 (2001). https://doi.org/10.1016/S03784371(01)00361-2
3. H. Kachkachi, D.A. Garanin, Euro. Phys. J. B 22, 291 (2001). https://doi.org/10.1007/
s100510170106
4. E.C. Stoner, E.P. Wohlfarth, Philos. Trans. R. Soc. London, Ser. A 240, 599 (1948)
5. L. Néel, Compt. Rend. Acad. Sci. 228, 664 (1949)
6. L. Néel, Compt. Rend. Acad. Sci. 237, 1468 (1953)
7. W.F. Brown, Phys. Rev. 135, 1677 (1963)
8. E.C. Stoner, E.P. Wohlfarth, IEEE Trans. Magn. 27, 3475 (1991)
9. W.F. Brown, IEEE Trans. Magn. 15, 1196 (1979)
10. A. Aharoni, Introduction to the Theory of Ferromagnetism (Oxford Science Pubs., 1996)
11. A. Aharoni, J. Appl. Phys. 83, 3432 (1998). https://doi.org/10.1063/1.367113
12. J. Langer, Phys. Rev. Lett. 21, 973 (1968)
13. J. Langer, Ann. Phys. (N.Y.) 54, 258 (1969)
14. W.T. Coffey, D.A. Garanin, D.J. McCarthy, Adv. Chem. Phys. 117, 483 (2001)
15. H. Kachkachi, J. Mol. Liquids 114, 113 (2004)
16. T.L.S.I. Denisov, P. Hänggi, Phys. Rev. Lett. 97, 227202 (2006)
17. G. Bertotti, I. Mayergoyz, C. Serpico, J. Appl. Phys. 91, 7556 (2002)
18. Z.Z. Sun, X.R. Wang, Phys. Rev. B 74, 132401 (2006)
Ò. Iglesias and H. Kachkachi
compare with experiments. It has thus been possible to figure out how the magnetization of the nanomagnet switches, to evaluate the corresponding relaxation time and
the switching magnetic field. The macroscopic models such as the Stoner-Wohlfarth
and Néel-Brown models have already been validated by experiments performed on
nanomagnets for which these models are applicable. In the opposite situation induced
by surface effects, we may say that only qualitative studies have been relatively successful, whereas any quantitative investigation still remains a challenge. However,
the fast progress in synthesis, characterization and measurement has allowed for an
unprecedented control of a whole set of properties of these nanomagnets and has
made it to possible to shrink the gap between theory and experiments. In particular,
the possibility of making well organised, nearly monodisperse assemblies of well
defined nanomagnets, offers a real potential for studying the competition between,
on one hand the intrinsic properties due to finite-size and boundary, shape and surface effects, and on the other the collective effects induced by mutual interactions
between the nanomagnets and by their interactions with the hosting medium. This
relatively favorable situation has triggered new impetus for further investigations of
NMs assemblies with a plethora of promising practical applications.
Acknowledgements Ò.I. acknowledges financial support form the Spanish MINECO (No. MAT201568772 and No. PGC2018-097789-B-I00), Catalan DURSI (No. 2017SGR0598) and European
Union FEDER Funds (una manera de hacer Europa), also CSUC for supercomputer facilities.
References
1. D.S. Schmool, H. Kachkachi, in Single-Particle Phenomena in Magnetic Nanostructures
(Chap. 4), Solid State Physics, vol. 66, ed. by R.E. Camley, R.L. Stamps (Academic Press,
2015), pp. 301 – 423. https://doi.org/10.1016/bs.ssp.2015.06.001. http://www.sciencedirect.
com/science/article/pii/S0081194715000053
2. H. Kachkachi, D.A. Garanin, Physica A 300, 487 (2001). https://doi.org/10.1016/S03784371(01)00361-2
3. H. Kachkachi, D.A. Garanin, Euro. Phys. J. B 22, 291 (2001). https://doi.org/10.1007/
s100510170106
4. E.C. Stoner, E.P. Wohlfarth, Philos. Trans. R. Soc. London, Ser. A 240, 599 (1948)
5. L. Néel, Compt. Rend. Acad. Sci. 228, 664 (1949)
6. L. Néel, Compt. Rend. Acad. Sci. 237, 1468 (1953)
7. W.F. Brown, Phys. Rev. 135, 1677 (1963)
8. E.C. Stoner, E.P. Wohlfarth, IEEE Trans. Magn. 27, 3475 (1991)
9. W.F. Brown, IEEE Trans. Magn. 15, 1196 (1979)
10. A. Aharoni, Introduction to the Theory of Ferromagnetism (Oxford Science Pubs., 1996)
11. A. Aharoni, J. Appl. Phys. 83, 3432 (1998). https://doi.org/10.1063/1.367113
12. J. Langer, Phys. Rev. Lett. 21, 973 (1968)
13. J. Langer, Ann. Phys. (N.Y.) 54, 258 (1969)
14. W.T. Coffey, D.A. Garanin, D.J. McCarthy, Adv. Chem. Phys. 117, 483 (2001)
15. H. Kachkachi, J. Mol. Liquids 114, 113 (2004)
16. T.L.S.I. Denisov, P. Hänggi, Phys. Rev. Lett. 97, 227202 (2006)
17. G. Bertotti, I. Mayergoyz, C. Serpico, J. Appl. Phys. 91, 7556 (2002)
18. Z.Z. Sun, X.R. Wang, Phys. Rev. B 74, 132401 (2006)