The magnetic anisotropy change of BaFe12-2xIrxCoxO19: a single-crystal neutron diffraction study of the accompanying atomic and magnetic structures

In this paper, we present the atomic and magnetic structures accompanying t he changer from axial to planar, of the magnetic anisotropy in BaFe12-2xIrx CoxO19 using magnetic measurements and single-crystal neutron diffraction. The magnetic measurements allowed us to determine the characteristic anisot ropy field H-0 and anisotropy constants k(i) for the different stages. Our structure refinements show that the change of magnetic anisotropy in BaFe12 -2xIrxCoxO19 leads, on a microscopic level, to a collective canting of the moments from 0 to 90 degrees through ferrimagnetic structures, which is in contrast to what has been observed up to now for other substituted single-c rystal hexaferrites. The peculiar change of the magnetic anisotropy in BaFe 12-2xIrxCoxO19 is correlated to the substitution of Fe3+ by Ir4+ on the 4e bipyramidal site. (C) 2000 Elsevier Science B.V. All rights reserved.