title: Theory of high-temperature multiferroicity in cupric oxide.
abstract: The incommensurate-commensurate phases reported in cupric oxide below 230 K are shown theoretically to realize an inverted sequence of symmetry-breaking mechanisms with respect to the usual sequence occurring in low-temperature multiferroic compounds. The sequence inversion results from a strong triggering-coupling mechanism between two antiferromagnetic order parameters inducing a first-order transition to the multiferroic phase. Such mechanism is favored by the large antiferromagnetic superexchange interactions, responsible of the high-T(N) temperature, and implies a preeminence of these interactions on the magnetocrystalline anisotropy. The magnetic structures of the equilibrium phases and the microscopic interactions giving rise to the polarization are determined.
authors.affiliation: Laboratory of Physics of Complex Systems, University of Picardie, 33 rue Saint-Leu, 80000 Amiens, France.
authors.forename: Pierre
authors.initials: P
authors.lastname: Tolédano
authors.forename: Naëmi
authors.initials: N
authors.lastname: Leo
authors.forename: Dmitry D
authors.initials: DD
authors.lastname: Khalyavin
authors.forename: Laurent C
authors.initials: LC
authors.lastname: Chapon
authors.forename: Tim
authors.initials: T
authors.lastname: Hoffmann
authors.forename: Dennis
authors.initials: D
authors.lastname: Meier
authors.forename: Manfred
authors.initials: M
authors.lastname: Fiebig