Dresden 2011 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe
TT: Fachverband Tiefe Temperaturen
TT 35: CE: Low-dimensional Systems - Materials 3
TT 35.3: Vortrag
Mittwoch, 16. März 2011, 14:30–14:45, HSZ 301
Magnons in the Quantum Dimer Antiferromagnet Sr3Cr2O8 — •Diana Lucia Quintero-Castro1,2, Bella Lake1,2, Elisa Maria Wheeler1, and Nazmul Islam1 — 1Helmholtz Zentrum Berlin, Berlin 14109, Germany — 2Institut für Festkörperphysik, Technische Universität Berlin, D-10623 Berlin, Germany
Sr3Cr2O8 consists of a three-dimensional frustrated arrangement of antiferromagnetically coupled pairs of Cr ions or dimers. The Cr ions are in the unusual 5+ valence state resulting in one electron in the 3d shell and a spin value of 1/2 while a tetrahedral crystal field ensures that this electron occupies the doubly degenerate eg orbitals. Below room temperature Sr3Cr2O8 undergoes a cooperative Jahn Teller distortion that lifts the orbital degeneracy so that only the 3z2-r2 orbital is occupied. The low temperature structure is characterized by monoclinic crystal symmetry and antiferro-orbital ordering. The transition also gives rise to spatially anisotropic exchange paths and results in three crystal twins. We have grown single crystals of Sr3Cr2O8 and have performed DC susceptibility measurements, high field magnetisation and powder and single crystal inelastic neutron scattering experiments. The data reveals a singlet ground state and gapped triplet excitations consisting of three modes, coming from the three crystal twins. Using a random phase approximation, we have extracted the magnetic exchange interactions within the dimer and between dimers. Sr3Cr2O8 is a candidate for the study of the critical properties in the quantum phase transition as the magnetic field can drive a Bose Einstein condensation of magnons.