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MA: Magnetismus

MA 37: Molecular Magnetism

MA 37.6: Vortrag

Freitag, 31. März 2006, 12:00–12:15, HSZ 403

Field-dependent magnetic paramaters in {Ni₄Mo₁₂} — •Mirko Brüger and Jürgen Schnack — Universität Osnabrück, Fachbereich Physik, Barbarastr. 7, D-49069 Osnabrück

Mo ^V ₁₂ O₃₀(µ ₂ − OH)₁₀ H ₂ {Ni^II(H₂O)₃ }₄ is a magnetic molecule which on first glance looks rather unspectacular since it comprises four Ni ions which are placed at the vertices of an almost ideal tetrahedron and connected by oxygen bridges. Thus one would expect that the magnetic energy levels are reasonably well described by an isotropic Heisenberg model with antiferromagnetic coupling. Preliminary experimental results, obtained by our experimental collaborators in Ames (USA) and Okayama (Japan), show a low-temperature magnetization curve (M vs. B) with increasing step size. The magnetization curve shows two equal steps at low fields and two larger steps of similar size at high fields, which are rounded of anisotropy. Even including biquadratic exchange and Dzyaloshinsnskii-Moriya interaction we were unable to describe the low-temperature magnetization curve. Furthermore low-field susceptibility and magneto-optical experiments of our collaborators in Ames and Knoxville (USA) portend small changes in the structure of the molecule with applied magnetic field.