Single crystalline ferrite garnet spheres with high-Q-resonance characteristics

 

Low-loss single crystalline magnetic garnet spheres with high Q resonance characteristics over a broad frequency range have been used commercially for microwave applications since more than two decades.

 

Example of a Y3(Fe, Ga)5O12 cube

Example of a Y3(Fe, Ga)5O12 cube

Optically polished sphere

Optically polished sphere

 

 

Manufacturing process

The single crystalline material is usually grown from flux melts. The preparation of optically polished spheres with diameters of around 0.3 mm is based on pieces in the shape of cubes (upper picture), which are sliced and diced from the single crystals. Finally, the cubes are shaped into spheres (lower picture) and their surfaces are polished to a high degree of perfection.

The saturation polarization 4pMs of the spheres is dependent on the substitution level of diamagnetic ions and can be determined as the distance between the (210) Walker and the homogeneous precession mode (left graph). Typical values of the full width of the half maximum of the ferromagnetic resonance ΔH are less than 1 Oe (right graph).

 

 

Microwave absorption as a function of the saturation polarization

Microwave absorption as a function of the saturation polarization 4πMs = 7.5(f – f0)/γ with f as frequency, f0 as resonance frequency, and γ gyromagnetic ratio for a Y3(Fe, Ga)5O12 sphere.

Microwave absorption in dependence on the magnetic field

Microwave absorption in dependence on the magnetic field ΔH = (f – f0)/γ with f as frequency, f0 as resonance frequency, and γ gyromagnetic ratio for a Y3(Fe, Ga)5O12 sphere.

 

Typical half-value widths for the ferromagnetic resonance line width ΔH are less than 1 Oe.

 

Applications

YIG single crystals are most commonly used for the construction of electronically tunable oscillators (YIG oscillator) and filters. For the set-up of such components magnetically tunable resonators are being deployed. As major frequency-determining component YIG single crystals are applied.

 

 

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