Commensurate to incommensurate magnetic phase transition in type-II multiferroic YBaCuFeO5
Yen-Chung Lai1,2*, Wei-Tin Chen2, Kirrily C. Rule3, Fang-Cheng Chou2,4,5, Chao-Hung Du1
1Department of Physics, Tamkang University, New Taipei city, Taiwan
2Center for Condensed Matter Sciences, National Taiwan University, Taipei, Taiwan
3Bragg Institute, ANSTO, NSW, Australia
4National Synchrotron Radiation Research Center, Hsinchu, Taiwan
5Taiwan Consortium of Emergent Crystalline Materials, Ministry of Science and Technology, Taipei, Taiwan
* presenting author:賴彥仲,
YBaCuFeO5 with FeO2/CuO2 planes has been reported to be a type-II multiferroic material, which implies the existence of intriguing couplings between the ferroelectricity and chiral magnetism. Using modified traveling solvent floating zone crystal growth method, we have been able to grow centimeter size high quality single crystal of YBaCuFeO5 which shows two magnetic transitions near TN1 = 450 K and TN2 = 170 K. Using neutron single crystal diffraction, we observed two antiferromagnetic phase transition at ~170 and 450 K in accordance with the magnetization data. The antiferromagnetic phase shows the magnetic reflections at (h/2, k/2, l/2), h, k, and l are odd. Upon cooling, at 170 K, the commensurate magnetic reflections were observed to become incommensurate with positions of (h/2, k/2, l/2±δ), where the incommensurability δ is temperature dependent. In addition, we also observed a magnetic diffuse scattering beside at the commensurate magnetic reflections at 200 K. This magnetic diffuse scattering is responsible for the formation of incommensurate reflections at low temperatures. Experiment was also conducted to study the magnetic field effects on the magnetic structure. Under the application of magnetic field, we also observed a magnetic soliton lattice, and a complicated magnetic phase diagram.

Keywords: Multiferroic, Magnetic structure, YBaCuFeO5