Dresden 2006 – wissenschaftliches Programm

Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe

MA: Magnetismus

MA 20: Poster: Films(1-36) Transp(37-56) Ex.Bias(57-67) Spindyn(68-80) Micromag(81-95) Particle(96-109) Imag.+Surface(110-113) Spinelectr(114-122) Theory+Micromag(123-131) Spinstr+Aniso(132-142) MagMat(143-156) Meas(157,158) MolMag+Kondo(159-162) Postdead(163-)

MA 20.160: Poster

Dienstag, 28. März 2006, 15:15–19:15, P1

Magnetism of multi-center Ni- and Fe-based molecular complexes: Pulsed magnetic fieldstudies — •R. Klingeler^1,2, V. Kataev¹, C. Golze^1,3, B. Büchner¹, A. Alfonsov¹, H. Klauss³, C. Mennerich³, M. Goiran², H. Rakoto², J.M. Broto², S. Demeshko⁴, G. Leibeling⁴, F. Meyer⁴, P. Körgerler⁵, J. Schnack⁶, and D.J. Price⁷ — ¹IFW Dresden — ²LNCMP Toulouse, France — ³TU Braunschweig — ⁴University Göttingen — ⁵Ames Laboratory,USA — ⁶University Osnabrück — ⁷University Glasgow, UK

We performed measurements of the high frequency/high field ESR and of the magnetisation in pulsed magnetic fields up to 55 T in order to investigate the ground state and the low lying excitations of several novel polynuclear complexes. In particular, we studied the 2-leg ladder compound Na₂Ni₂(C₂O₄)₃(H₂O)₂, the [L₂Ni₄(N₃)(O₂CR)₄](ClO₄)-type tetranuclear-Ni(II) molecular complex and the giant Keplerate magnetic molecules {Mo₇₂Fe₃₀} coupled to a square lattice. In Ni-oxalate, the M(B) and ESR data imply spin level crossings at ∼29 T and ∼54 T. We find a non-magnetic ground state, sharp steps of the magnetisation at the spin-level crossings and a plateaux-like behaviour between. In the tetranuclear Ni(II) complex, our data imply a spin-level crossing at ∼25 T from a non-magnetic to a magnetic state. However, our M(B) data show a finite susceptibility at T=1.5 K and low fields which indicates a more complex ground state than the simple singlet state. For the giant Keplerate sample we concentrate on the intramolecular interactions. In particular, our data reveal signatures of long range AFM correlations and AFM order, respectively, at low T.