Evolution of the magnetic and structural properties of Fe${}_{1-x}$Co${}_x$V${}_2$O${}_4$

Abstract

The magnetic and structural properties of single crystal Fe${}_{1-x}$Co${}_x$V${}_2$O${}_4$ samples have been investigated by performing specific heat, susceptibility, neutron diffraction, and X-ray diffraction measurements. As the orbital-active Fe${}^{2+}$ ions with larger ionic size are gradually substituted by the orbital-inactive Co${}^{2+}$ ions with smaller ionic size, the system approaches the itinerant electron limit with decreasing V-V distance. Then, various factors such as the Jahn-Teller distortion and the spin-orbital coupling of the Fe${}^{2+}$ ions on the A sites and the orbital ordering and electronic itinerancy of the V${}^{3+}$ ions on the B sites compete with each other to produce a complex magnetic and structural phase diagram. This phase diagram is compared to those of Fe${}_{1-x}$Mn${}_x$V${}_2$O${}_4$ and Mn${}_{1-x}$Co${}_x$V${}_2$O${}_4$ to emphasize several distinct features.

9 pages, 9 figures