Influence of ligand surrounding and crystal lattice dimensionality on the magnetic anisotropy of 3d transition metal ions

Herak, Mirta (2009) Influence of ligand surrounding and crystal lattice dimensionality on the magnetic anisotropy of 3d transition metal ions. Doctoral thesis, Faculty of Science > Department of Physics.

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Abstract

The magnetic properties of the low-dimensional CuGeO3 and CuSb2O6, three-dimensional Bi2CuO4 and Cu3TeO6 , and of Cu2Te2O5X2 (X=Cl, Br) were investigated by the dc magnetic susceptibility measurement and torque magnetometry. Magnetism in these compounds comes from Cu2+ ion with an unpaired electron with spin S = 1/2 in a 3d shell. In spin - Peierls system CuGeO3 a small amount of defects was detected with the susceptibility following the χdef = AT-α law at low temperatures with a α ≈ 0.7. This suggests breaking of regular chains and existence of more than one exchange energy on the chain. In the one - dimensional CuSb2O6 which orders antiferromagnetically (AFM) the interchain interaction Jinter is weak compared to the intrachain J, Jinter = 0.05 J, and the anisotropy of the exchange energy is also small, 1%J. A combination of the measured angular dependence of torque and phenomenological approach to the anisotropy energy shows that the symmetry in Bi2CuO4 is described by the easy plane anisotropy with two perpendicular spin (S) domains, and not the easy axis anisotropy. Similar approach shows that Cu3TeO6, a system with a new type of 3D magnetic lattice, has cubic symmetry in the AFM state with four AFM S domains. In Cu2Te2O5X2 (X=Cl, Br) systems with the crystallographically isolated spin tetrahedra the Dzyaloshinskii-Moriya anisotropic interaction is detected. The AFM ordered state has two perpendicular AFM domains which can be repopulated by applying the magnetic field. The effective magnetic moment is smaller for X=Br than X=Cl.

Item Type: Thesis (Doctoral thesis)
Keywords: magnetic susceptibility, magnetic anisotropy, copper oxides, low dimensional lattices, ligand surrounding of magnetic ions, superexchange
Supervisor: Miljak, Marko
Date: 5 November 2009
Number of Pages: 183
Subjects: NATURAL SCIENCES > Physics
Divisions: Faculty of Science > Department of Physics
Depositing User: Gordana Stubičan Ladešić
Date Deposited: 22 Dec 2013 00:00
Last Modified: 29 Oct 2015 08:06
URI: http://digre.pmf.unizg.hr/id/eprint/47

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