Neutron diffraction and magnetic properties of Ba2Co2Fe12O22: Co2Y

Polycrystalline Y-type barium cobalt ferrite (Ba2Co2Fe12O22; Co2Y) was synthesized using by the conventional ceramic method. At temperatures below 260 K, the crystal structure of Co2Y was determined to be hexagonal with the space group . It showed a soft ferrimagnetic behavior with H (c) = 113 Oe at 297 K and the N,el temperature (T (N) ) was determined to be 615 K. Most of the super-lattice peaks of Co2Y coming from the spin structure decreased with increasing temperature. However, the super-lattice peak at 21.8A degrees increased with increasing temperature at temperatures above 200 K. In addition, we observed a change in the slope of the zero-field cooled magnetization under a low field of 0.01 T at 215 K due to a magnetic structure transition from a helical to a ferrimagnetic spin structure.