Magnetic Structure of (Ba_1-xSr_x)₂Zn₂Fe_{1 2}O₂₂(x=0-1.0)

Abstract

Neutron and X-ray diffraction studies and magnetization measurements were carried out on single crystals of (Ba 1- x Sr x ) 2 Zn 2 Fe 12 O 22 . The substitution of Ba by Sr produces two effects on the crystal structure: a lattice deformation around the Sr ions and a redistribution of the Zn and Fe ions in the tetrahedral sites. The magnetic structure is analyzed in consideration of these effects: Spins are bunched in the form of ferrimagnet in the every (T 1/2 ST 1/2 ) block and the bunched spins make an angle φ 0 between the adjacent (T 1/2 ST 1/2 ) blocks. At 294 K, the turn angles φ 0 's are found to be 0^° (ferromagnetic), 0^°<φ 0 <180^° (helical) and 180° (antiferromagnetic) for 0≤ x ≤0.5, 0.5< x <0.8 and \(0.8{\lesssim}x{\leq}1.0\), respectively. A brief discussion on the exchange interaction of this spin system is given.