Classical and quantum magnetic relaxation in selected nanomagnets

Pajić, Damir (2008) Classical and quantum magnetic relaxation in selected nanomagnets. Doctoral thesis, Faculty of Science > Department of Physics.

Language: Croatian

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We investigated the magnetic properties of three classes of nanomagnets: magnetic nanoparticles CuxFe3-x04, single-molecule magnets Mn12-acetate and Mn12-formate , and magnetic clusters within amorphous alloy Hf100-xFex. Measurements of the temperature dependence of the zero field cooled and field cooled magnetization, magnetic hysteresis looops, slow relaxation of magnetization on the time scale of experiment and other, all point to the thermal activation of superparamagnetic moments over the potential anisotropy barriers, which is called classicaI relaxation. In Mn12-acetate the steps on hysteresis loops, resonant behaviour of the field dependence of relaxation time and anomalies in the time relaxation of magnetization were observed. All of this is explained by the quantum tunnelling of spin of the molecule. For the nanoparticles and magnetic clusters within alloy the distribution of magnetic moments over anisotropy barrier heights were determined, as well as the effective anisotropy density in nanoparticles and the size of magnetic nano-clusters in the alloy. The complex magnetic structure of nanoparticles induced by the surface effects was observed. All these features make the observation of the quantum tunnelling of magnetization more complex.

Item Type: Thesis (Doctoral thesis)
Keywords: nanomagnets ; relaxation of magnetization ; quantum tunnelling ; single-molecule magnet Mn12 ; magnetic nanoparticles ; magnetic clusters in amorphous alloy ; magnetic properties
Supervisor: Zadro, Krešo
Date: 17 March 2008
Number of Pages: 179
Subjects: NATURAL SCIENCES > Physics
Divisions: Faculty of Science > Department of Physics
Depositing User: Gordana Stubičan Ladešić
Date Deposited: 14 May 2014 15:23
Last Modified: 14 May 2014 15:23

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