Effect of manganese addition on the microstructure and electromagnetic properties of YIG

Y 3 Mn x Fe 4.85- x O 12 ( x =0, 0.02, 0.04, 0.06, 0.08 and 0.1) garnet ferrites (YMnIG) were prepared by conventional solid-state reaction method in air atmosphere. The effect of Mn addition on the microstructure and electromagnetic properties of YIG were investigated by means of techniques such as X-ray diffraction, scanning electron microscopey, network analyzer, hysteresigraph, magnetic balance and electron paramagnetic resonance spectrometry. Pure garnet phase of Y 3 Fe 5 O 12 was identified for all the samples, except for minor YFeO 3 phase appearing in the sample with x =0.06. The addition of Mn showed little influence on the dielectric constant of YIG, which varied between 14.2 and 14.5. Substituting Mn n + for Fe n + in YIG decreased the total amount of Fe ions, inhibited the reduction of Fe 3+ and promoted the grain growth of garnet phase, which led to the decrease in dielectric loss and coercivity. Because the amount of Mn 3+ ions in octahedral sites increased with Mn concentration, the saturation magnetization showed a slight decrease firstly and then increased notably. The addition of Mn could also increase the remanence ratio of YIG ferrites by decreasing the magnetostriction constant γ 111 . Therefore, doping Mn into YIG ferrites with proper quantity could improve electromagnetic properties of YIG significantly. The YMnIG ferrite with x =0.08, i.e., Y 3 Mn 0.08 Fe 4.77 O 12 , showed the optimum electromagnetic properties: ɛ r =14.2, tan δ e =1.5×10 −4 , H c =36 A/m, 4π M S =192 mT, B r / B s =0.84, Δ H =6.8 KA/m.