Application range of Yttrium Iron Garnet (YIG) Yttrium–iron garnet (Y2Fe5O12) is a soft magnetic ferrite widely used in frequency-selective and non-reciprocal devices. It is most suitable for applications involving which frequency range?

Introduction / Context:
Yttrium–iron garnet (YIG) is a ferrimagnetic material prized for its very low microwave losses and tunability under magnetic bias. It underpins microwave filters, circulators, isolators, oscillators, and magnetostatic wave devices in RF and microwave engineering.

Given Data / Assumptions:

• Material: YIG, a ferrite with narrow ferromagnetic resonance linewidth.
• Operating environment: RF/microwave frequencies with magnetic bias fields.
• Soft magnetic behavior (low coercivity) suitable for high-frequency magnetization dynamics.

Concept / Approach:

Ferrimagnetic resonance and magnetostatic spin waves in YIG occur in the hundreds of megahertz to gigahertz range. The extremely low damping (small linewidth) allows high-Q microwave components. At power-line or audio frequencies, ordinary soft magnetic steels or ferrites suffice; YIG is unnecessary and not optimized for such low frequencies.

Step-by-Step Solution:

Verification / Alternative check:

Commercial YIG-tuned filters and oscillators commonly operate from about 100 MHz up to multi-GHz. This validates the selected option.

Why Other Options Are Wrong:

DC and 50 Hz (a, b) are far below the microwave regime; a few kHz (c) is still audio/low RF; terahertz (e) exceeds typical YIG device operation and material resonances.

Common Pitfalls:

Confusing general ferrites used up to a few MHz with specialized YIG components; assuming any magnetic material works equally well across all frequencies.

Final Answer:

Alternating current of a few hundred megahertz