Fluctuations of spiral spins in the double-perovskite ferrite YBaCuFeO5
Chao-Hung Du1,2*, Yu-Hui Liang1, Chun-Hao Lai1, K. C Rule3, C.-W. Wang4, S. Yano4
1Department of Physics, Tamkang University, Tamsui Dist., Taiwan
2Research Center for X-ray Science, Tamkang University, Tamsui Dist., Taiwan
3Australian Center for Neutron Scattering, ANSTO, Australia
4Neutron Group, National Synchrotron Radiation Research Center, Taiwan
* Presenter:Chao-Hung Du, email:chd@gms.tku.edu.tw
The double-perovskites exhibit many fundamentally interesting chemical and physical properties; they can have electronic structures raging from insulator, metallic, halfmetallic to superconductor; they can also have different magnetic order parameters; or even simultaneously containing the multiple order parameters, such as multiferroicity. The double-perovskite ferrite YBaCuFeO5 (YBCFO) is such a material to show a rich phase diagram. Using a modified floating zone growth method, we are able to grow the high-quality single crystal of YBCFO for the detailed studies using neutron scattering. Using neutron powder and single crystal diffraction, YBCFO was observed to show a commensurate-incommensurate magnetic transition at TN~ 175 K. This incommensurate phase develops into a spiral spin ordering with a propagating vector along c-axis. Further using neutron TOF and triple-axis spectrometers, we observed that the spiral spin ordering shows a very unusual dispersion behavior as a function of temperature, which could be the consequence of a strong coupling between the spin moments of Fe3+ and Cu2+ and their dz orbitals.

Keywords: spiral spin ordering, magnetic excitation, inelastic neutron scattering