title: Evidence for a subtle structural symmetry breaking in EuB(6).
abstract: This work presents a systematic Raman scattering study and first-principles calculations for the EuB(6) system. Evidence for the presence of an incipient (∼1 × 10(-4) Å) tetragonal symmetry break of its crystalline structure was found. Forbidden Raman modes at ω(fRm(1))∼1170 cm(-1), ω(fRm(2))∼1400 cm(-1), and ω(fRm(3))∼1500  cm(-1) were observed. The tetragonal symmetry of ω(fRm(2)) and ω(fRm(3)) together with spin-polarized first-principles simulations of the structural and magnetic properties fully support such a break of symmetry. Our data and calculations explain the occurrence of ferromagnetism in Eu hexaborides, previously reported.
authors.affiliation: Centro de Ciências Naturais e Humanas, Universidade Federal do ABC, Rua Santa Adélia 166, 09210-170, Santo André, São Paulo, Brazil.
authors.forename: H
authors.initials: H
authors.lastname: Martinho
authors.forename: C
authors.initials: C
authors.lastname: Rettori
authors.forename: G M
authors.initials: GM
authors.lastname: Dalpian
authors.forename: J L F
authors.initials: JL
authors.lastname: da Silva
authors.forename: Z
authors.initials: Z
authors.lastname: Fisk
authors.forename: S B
authors.initials: SB
authors.lastname: Oseroff