title: Magnetic ordering and dielectric relaxation in the double perovskite YBaCuFeO5.
abstract: Using magnetization, dielectric constant, and neutron diffraction measurements on a high quality single crystal of YBaCuFeO5(YBCFO), we demonstrate that the crystal shows two antiferromagnetic transitions at [Formula: see text] K and [Formula: see text] K, and displays a giant dielectric constant with a characteristic of the dielectric relaxation at TN2. It does not show the evidence of the electric polarization for the crystal used for this study. The transition at TN1corresponds with a paramagnetic to antiferromagnetic transition with a magnetic propagation vector doubling the unit cell along three crystallographic axes. Upon cooling, at TN2, the commensurate spin ordering transforms to a spiral magnetic structure with a propagation vector of ([Formula: see text] [Formula: see text] [Formula: see text]), where [Formula: see text], [Formula: see text], and [Formula: see text] are odd, and the incommensurability δ is temperature dependent. Around the transition boundary at TN2, both commensurate and incommensurate spin ordering coexist.
authors.affiliation: National Synchrotron radiation Research Center, Hsinchu 30076, Taiwan.
authors.forename: Yen-Chung
authors.initials: YC
authors.lastname: Lai
authors.forename: Chao-Hung
authors.initials: CH
authors.lastname: Du
authors.forename: Chun-Hao
authors.initials: CH
authors.lastname: Lai
authors.forename: Yu-Hui
authors.initials: YH
authors.lastname: Liang
authors.forename: Chin-Wei
authors.initials: CW
authors.lastname: Wang
authors.forename: Kirrily C
authors.initials: KC
authors.lastname: Rule
authors.forename: Hung-Cheng
authors.initials: HC
authors.lastname: Wu
authors.forename: Hung-Duen
authors.initials: HD
authors.lastname: Yang
authors.forename: Wei-Tin
authors.initials: WT
authors.lastname: Chen
authors.forename: G J
authors.initials: GJ
authors.lastname: Shu
authors.forename: F-C
authors.initials: FC
authors.lastname: Chou