Short-range magnetic ordering in the geometrically frustrated layered compound YBaCo_4O_7 with an extended Kagome structure

摘要

Structural and magnetic properties of the geometrically frustrated layered compound YBaCo_4O_7 have been studied by magnetization and neutron diffraction. A layered type crystal structure, with alternating tetrahedral layers of Kagome and triangular types, along the c axis (hexagonal symmetry, space group P6_3mc) has been found. The oxygen content of the present compound was determined by iodometric titration to be 7.00 ± 0.01. Presence of a short-range antiferromagnetic ordering (below T_N ~ 110 K) has been concluded from the appearance of an addition broad magnetic peak (at Q ~ 1.35 A~(-1)) in the neutron diffraction pattern. A staggered chiral type (√3 × √5) spin structure in the Kagome layers has been found. Presence of a significant magneto-structural coupling is concluded from the changes in lattice parameters across the magnetic ordering temperature T_n ~ 110 K.