title: Novel multiferroic state and ME enhancement by breaking the AFM frustration in LuMn1-xO3.
abstract: This study provides a comprehensive insight into the effects of controlled off-stoichiometry on the structural and multiferroic properties of the hexagonal manganite LuMn1-xO3+δ(x = 0.02; δ ∼ 0), supported by neutron powder diffraction measurements confirming single phase P63cm symmetry and evidencing a relevant ferromagnetic component, below TN∼ 90 K, which breaks the archetypal geometrically frustrated antiferromagnetic state typically ascribed to LuMnO3. The perturbations in the triangular disposition of spins prompt an additional electric polarization contribution and a clear enhancement of the magnetoelectric coupling which are in good agreement with the results of first principles calculations. In addition, Raman spectroscopy, dielectric permittivity, pyroelectric current and magnetic measurements as a function of temperature point out the precursor effects of the magnetic phase transitions involving a strong coupling between spins, lattice and electric order, even above the Néel temperature.
authors.affiliation: Physics Department & CICECO-AIM, Aveiro University, 3810-193 Aveiro, Portugal. ffigueiras@ua.pt and IFIMUP and IN, Institute of Nanoscience and Nanotechnology, Dep de Física e Astronomia da Universidade do Porto, 4169-007 Porto, Portugal.
authors.forename: F G
authors.initials: FG
authors.lastname: Figueiras
authors.affiliation: Physics Department & CICECO-AIM, Aveiro University, 3810-193 Aveiro, Portugal. ffigueiras@ua.pt and National Research University of Electronic Technology "MIET", Zelenograd, Moscow, Russia and Scientific and Practical Materials Research Centre, National Academy of Sciences of Belarus, Minsk, Belarus.
authors.forename: D
authors.initials: D
authors.lastname: Karpinsky
authors.affiliation: Centro de Química-Vila Real, Departamento de Química, ECVA, Universidade de Trás-os-Montes & Alto-Douro, 5001-801 Vila Real, Portugal.
authors.forename: P B
authors.initials: PB
authors.lastname: Tavares
authors.affiliation: Physics Department & CICECO-AIM, Aveiro University, 3810-193 Aveiro, Portugal. ffigueiras@ua.pt.
authors.forename: J N
authors.identifier: http://orcid.org/0000-0002-9057-378X
authors.initials: JN
authors.lastname: Gonçalves
authors.affiliation: IFIMUP and IN, Institute of Nanoscience and Nanotechnology, Dep de Física e Astronomia da Universidade do Porto, 4169-007 Porto, Portugal.
authors.forename: S
authors.initials: S
authors.lastname: Yañez-Vilar
authors.affiliation: Quantum Condensed Matter Div., Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831, USA.
authors.forename: A F
authors.initials: AF
authors.lastname: Moreira Dos Santos
authors.affiliation: Helmholtz-Zentrum Berlin, Hahn-Meitner-Platz 1, 14109 Berlin, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Franz
authors.affiliation: Helmholtz-Zentrum Berlin, Hahn-Meitner-Platz 1, 14109 Berlin, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Tovar
authors.affiliation: IFIMUP and IN, Institute of Nanoscience and Nanotechnology, Dep de Física e Astronomia da Universidade do Porto, 4169-007 Porto, Portugal.
authors.forename: J
authors.initials: J
authors.lastname: Agostinho Moreira
authors.affiliation: Physics Department & CICECO-AIM, Aveiro University, 3810-193 Aveiro, Portugal. ffigueiras@ua.pt.
authors.forename: V S
authors.initials: VS
authors.lastname: Amaral