Block magnetism coupled with local distortion in the iron-based spin-ladder compound BaFe2Se3

Abstract

Magnetism in the insulating BaFe${}_2$Se${}_3$ was examined through susceptibility, specific heat, resistivity and neutron diffraction measurements. After formation of a short-range magnetic correlation, a long-range ordering was observed below $T_{\mathrm{N}}\sim 255$ K. The transition is obscured by bulk properties. Magnetic moments ($\parallel a$) are arranged to form a Fe${}_4$ ferromagnetic unit, and each Fe${}_4$ stacks antiferromagnetically. This block magnetism is of the third type among magnetic structures of ferrous materials. The magnetic ordering drives unusually large distortion via magnetoelastic coupling.

5 pages, 4 figures