title: Direct observation of spontaneous weak ferromagnetism in the superconductor ErNi2B2C.
abstract: Neutron measurements show that superconducting ErNi2B2C (T(C) = 11 K) develops antiferromagnetic spin density wave magnetic order (T(N) = 6 K), which squares up with decreasing temperature yielding a series of higher-order magnetic Bragg peaks with odd harmonics. Below T(WFM) = 2.3 K where magnetization indicates a net moment develops, even-order Bragg peaks develop which low field (approximately 3 Oe) polarized beam measurements show are magnetic in origin. The data directly demonstrate the existence of a net magnetization with a periodicity of 20a, confirming the microscopic coexistence of spontaneous weak ferromagnetism with superconductivity.
authors.affiliation: National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA.
authors.forename: S M
authors.initials: SM
authors.lastname: Choi
authors.forename: J W
authors.initials: JW
authors.lastname: Lynn
authors.forename: D
authors.initials: D
authors.lastname: Lopez
authors.forename: P L
authors.initials: PL
authors.lastname: Gammel
authors.forename: P C
authors.initials: PC
authors.lastname: Canfield
authors.forename: S L
authors.initials: SL
authors.lastname: Bud'ko