Cooperation effect of indium and vanadium co-doped into bismuth-iron garnets on magnetic properties

Abstract For achieving tunable saturation magnetization and line width, different cations were doped into the YIG-based garnets, which the standard molecular formula could be expressed as A₃[Fe_2−xM_x](Fe_3−yN_y)O₁₂. Most researchers have reported a single rule of one element doping (x or y) on its magnetic properties. However, the cooperation effect of x + y to the magnetic contribution was not clearly clarified. In this work, multi-doped bismuth-iron garnets {Bi_0.84Ca_2.16}[Fe_2−xIn_x](Fe_3−yV_y)O₁₂ (x = 0.72–0.14 and y = 1.24–1.38) with low saturation magnetizations (4πM _s = 200–600 Gs at 298 K) were prepared by a conventional fluxing agent method. The cooperation effect of In³⁺ and V⁵⁺ co-doped into bismuth-iron garnets (BIG) on their structures and magnetic properties were systematically investigated using XPS, TEM and VSM. It could be found that the total doped concentration (x + y) was decreasing regardless of the increasing V concentration (y) and decreasing In concentration (x). As-synthesized BIG presented a well single-crystal structure, and the lattice spacing was decreasing with the decrease of x + y in accompanying with the transition of dislocations from point defects to edge dislocations. Both linear increase of Curie temperature and 4πM _s with the decrease of x + y was revealed. The mechanism could be attributed that the doped non-magnetic ions could reduce the average nearest-neighbor coordination irons for oxygen ions and weaken the anti-ferromagnetic super-exchange interactions among the magnetic ions within the structure, namely dilution effect. By comparison, the total concentraions were higher than that of previous works, which the tailorable 4πM _s of ferrite was not reported. Here we revealed the controllable 4πM _s with higher total concentrations (x + y ≥ 1.52). These findings will be provided more opportunities for applications in microwave devices.