title: In-plane ferromagnetism in charge-ordering Na0.55CoO2.
abstract: The magnetic and transport properties are systematically studied on the single crystal Na(0.55)CoO2 with the resistivity divergence below 50 K. A weak ferromagnetic ordering is observed in susceptibility below 20 K with the magnetic field parallel to the Co-O plane, while no such ferromagnetic ordering is observed with the field perpendicular to the Co-O plane. It gives evidence for the existence of in-plane ferromagnetism below 20 K. The observed magnetoresistance of 30% at the field of 6 T at low temperatures indicates an unexpectedly strong spin-charge coupling in the triangle lattice NaxCoO2 system.
authors.affiliation: Hefei National Laboratory for Physical Science at Microscale and Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China.
authors.forename: C H
authors.initials: CH
authors.lastname: Wang
authors.forename: X H
authors.initials: XH
authors.lastname: Chen
authors.forename: T
authors.initials: T
authors.lastname: Wu
authors.forename: X G
authors.initials: XG
authors.lastname: Luo
authors.forename: G Y
authors.initials: GY
authors.lastname: Wang
authors.forename: J L
authors.initials: JL
authors.lastname: Luo