title: Unprecedented robust antiferromagnetism in fluorinated hexagonal perovskites.
abstract: The diversification of antiferromagnetic (AFM) oxides with high Néel temperature is of fundamental as well as technical interest if one considers the need for robust AFM in the field of spin-tronics (exchange bias, multiferroics, etc.). Within the broad series of so-called hexagonal perovskites (HP), the existence of face-sharing octahedral units drastically lowers the strength of magnetic exchanges as compared to corner-sharing octahedral edifices. Here, we show that the partial introduction of F(-) in several Fe-based HP types leads to a drastic increase of the AFM ordering close to the highest values reported in iron oxides (T(N) ≈ 700 K). Our experimental results are supported by ab initio calculations. The T(N) increase is explained by the structural effect of the aliovalent F(-) for O(2-) substitution occurring in preferred anionic positions: it leads to local changes of the Fe-O-Fe connectivity and to chemical reduction into predominant Fe(3+), both responsible for drastic magnetic changes.
authors.affiliation: Université Lille Nord de France, UCCS, CNRS UMR 8181, ENSCL-USTL, Villeneuve d'Ascq, France.
authors.forename: Mihai
authors.initials: M
authors.lastname: Sturza
authors.forename: Houria
authors.initials: H
authors.lastname: Kabbour
authors.forename: Sylvie
authors.initials: S
authors.lastname: Daviero-Minaud
authors.forename: Dmitry
authors.initials: D
authors.lastname: Filimonov
authors.forename: Konstantin
authors.initials: K
authors.lastname: Pokholok
authors.forename: Nicolas
authors.initials: N
authors.lastname: Tiercelin
authors.forename: Florence
authors.initials: F
authors.lastname: Porcher
authors.forename: Laurent
authors.initials: L
authors.lastname: Aldon
authors.forename: Olivier
authors.initials: O
authors.lastname: Mentré