Dresden 2006 – scientific programme
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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
Tuesday, March 28, 2006, 15:15–19:15, P1
Magnetism of multi-center Ni- and Fe-based molecular complexes: Pulsed magnetic fieldstudies — •R. Klingeler1,2, V. Kataev1, C. Golze1,3, 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.