Neutron diffraction and exchange interaction on CoAlxFe2-xO4 (x=0.1,0.2)

Magnetic and structural properties of CoAlxFe2-xO4 (x=0.1,0.2) have been studied with X-ray, neutron diffraction, and Moessbauer spectroscopy. Neutron diffraction pattern at 10 K reveals a cubic spinel of Fd3m with ferrimagnetic order. Debye temperatures of the tetrahedral (A) and octahedral (B) site for CoAl0.2Fe1.8O4 are found to be ΘA=709 and ΘB=197 K, respectively. The A-B and A-A superexchange interactions of CoAl0.2Fe1.8O4 are antiferromagnetic with the strengths of JA-B=-21.3 and JA-A=-19.6 kB, respectively, while the B-B interaction is ferromagnetic with a strength of JB-B=4.8 kB