arXiv subjects

G. Aeppli

Publications and source records attributed to G. Aeppli.

76 records · Page 5Linked to original sources

arXiv1996

Dramatic Switching of Magnetic Exchange in a Classic Transition Metal Oxide: Evidence for Orbital Ordering

Spin correlations in metallic and insulating phases of $V_2O_3$ and its derivatives are investigated using magnetic neutron scattering. Metallic samples have incommensurate spin correlations varying little with hole doping. Paramagnetic insulating samples have spin correlations only among near neighbors. The transition from either of these phases into the low temperature insulating antiferromagnetic phase is accompanied by an abrupt change of dynamic magnetic short range order. Our results support the idea that the transition into the antiferromagnetic insulator is also an orbital ordering transition.

cond-mat.str-el↗

arXiv1996

New magnetic coherence effect in superconducting La_{2-x}Sr_{x}CuO_{4}

We have used inelastic neutron scattering to examine the magnetic fluctuations at intermediate frequencies in the simplest high temperature superconductor, La_{2-x}Sr_{x}Cu_{4}. The suppression of the low energy magnetic response in the superconducting state is accompanied by an increase in the response at higher energies. Just above a threshold energy of ~7 meV there is additional scattering present below T_{c} which is characterised by an extraordinarily long coherence length, in excess of 50 Å.

cond-mat↗

arXiv1996

Neutron Scattering Studies of Heavy Fermion Systems

We review the results of recent studies of the elastic and inelastic neutron scattering from a variety of heavy fermion compounds. This class of materials exhibits a rich variety of ground states: antiferromagnetically ordered, superconducting, semiconducting, and paramagnetic. Neutron scattering from single crystals and powders has been a productive tool for probing the magnetic order and fluctuations in all four cases. This review deals with work on UPt_3, UPd_2Al_3, UNi_2Al_3, UNi_4B, CeNiSn, Y_{1-x}U_xPd_3, and UCu_{5-x}Pd_x.

cond-mat↗

arXiv1996

High-Frequency Spin Waves in YBa2Cu3O6.15

Pulsed neutron spectroscopy is used to make absolute measurements of the dynamic magnetic susceptibility of insulating YBa2Cu3O6.15. Acoustic and optical modes, derived from in- and out-of-phase oscillation of spins in adjacent CuO2 planes, dominate the spectra and are observed up to 250 meV. The optical modes appear first at 74 meV. Linear-spin-wave theory gives an excellent description of the data and yields intra- and inter-layer exchange constants of J_parallel =125 meV and J_perp = 11 meV respectively and a spin-wave intensity renormalization Z_chi = 0.4.

cond-mat↗