Regensburg 2002 – scientific programme

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MA: Magnetismus

MA 12: Quasiniedrigdimensionale Systeme

MA 12.1: Talk

Wednesday, March 13, 2002, 17:30–17:45, H22

Macroscopic magnetization jumps due to independent magnons on frustrated quantum spin lattices — •Jürgen Schnack¹, Heinz-Jürgen Schmidt¹, Jörg Schulenburg², Johannes Richter², and Andreas Honecker³ — ¹Universität Osnabrück, 49069 Osnabrück — ²Universität Magdeburg, P.O. Box 4120, 39016 Magdeburg — ³TU Braunschweig, Mendelssohnstr. 3, 38106 Braunschweig

For a class of frustrated spin lattices including the kagomé lattice and the recently synthesized magnetic molecule {Mo₇₂Fe₃₀} we construct exact eigenstates consisting of several independent, localized one-magnon states. Under rather general conditions it can be proven that these states are ground states in Hilbert subspaces of high total magnetic quantum numbers, thus they are relevant at high magnetic fields. If the maximal number of local magnons scales with the number of spins in the system, which is the case for the kagomé lattice, the effect persists in the thermodynamic limit and gives rise to a macroscopic jump in the zero-temperature magnetization curve just below the saturation field. The effect decreases with increasing spin quantum number and vanishes in the classical limit. Thus it is a true macroscopic quantum effect.