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
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概要
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Y free polycrystalline garnets, which composition is given by the formula Ca<SUB>3-y</SUB>Bi<SUB>y</SUB>Fe<SUB>3.5-0.5x+0.5y</SUB> Ge<SUB>x</SUB>V<SUB>1.5-0.5x-0.5y</SUB>Oi<SUB>12</SUB>, are synthesized with standard ceramic techniques.<BR>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<SUP> 4+</SUP> ion substitution reduces the porosity with 0≤x≤0.3 and decreases the anisotropy constant K<SUB> 1</SUB> with x≥0.5 since a part of Ge<SUP> 4+</SUP> 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<SUB> 1</SUB>/Ms values of single crystals.<BR>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.
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