Ge置換およびホットプレスによるCa-V-Biガーネットの低ΔH化

抄録

Y free polycrystalline garnets, which composition is given by the formula Ca_3-yBi_yFe_{3.5-0.5x+0.5y} Ge_xV_{1.5-0.5x-0.5y}Oi₁₂, are synthesized with standard ceramic techniques.
The materials whose Tc are higher than that of Al-substituted YIG for the same 4πMs (≤800G) and dH values can be obtained. The Ge ⁴⁺ ion substitution reduces the porosity with 0≤x≤0.3 and decreases the anisotropy constant K ₁ with x≥0.5 since a part of Ge ⁴⁺ ions enter into 16a sites of garnet structure. Only 25% of entire ΔH of the garnets with 0≤x≤0.3 are due to anisotropy broadening according to the spinwave theory using observed K ₁/Ms values of single crystals.
Using proper hot-pressing techniques, the porosity can be reduced to nearly zero. Small linewidth materials with ΔH=12Oe and ΔH=6Oe are obtained with the composition of (x=0.3, y=0.2) and (x=0.5, y=0.2), respectively.