Magnetic Structure Change in Ba₂Mg₂Fe₁₂O₂₂

Abstract

Neutron diffraction study was carried out on a single crystal of Ba₂Mg₂Fe₁₂O₂₂. The magnetic structure of Ba₂Mg₂Fe₁₂O₂₂ changes at 195 K, collinear ferrimagnet above 195 K and proper helix below 195 K. The helix is propagated along the c-axis by rotations of the large and small spin-bunches. The turn angle of the helix is 59.6° at 77 K and rapidly decreases as the temperature approaches 195 K. Results are discussed from a point of view of the exchange interactions.