Magnetic shielding is essential in applications where stray magnetic fields cause interference—from medical devices and sensitive electronics to audio equipment and industrial sensors. Unlike electric field shielding, magnetic shielding requires high-permeability materials to redirect and absorb magnetic flux.
This guide covers magnetic shielding principles, material selection, and practical design techniques.
Shaanxi SiRui Technology Co., Ltd. supplies nanocrystalline and permalloy shielding materials for magnetic shielding applications. Contact: sales@sirui-tech.com | Web: www.sirui-tech.com
1. How Magnetic Shielding Works
Magnetic shielding works by providing a low-reluctance path for magnetic flux, diverting it around the protected area. The shield material must have high permeability to attract and guide flux, high saturation to handle the field without saturating, and appropriate thickness.
2. Shielding Materials
| Material | Permeability (μi) | Bsat | Best For |
|---|---|---|---|
| Mu-metal (80% Ni-Fe) | 50,000–100,000 | 0.8 T | Low-field, low-frequency |
| Nanocrystalline | 30,000–80,000 | 1.2 T | Versatile, cost-effective |
| Silicon steel | 1,000–5,000 | 1.8–2.0 T | High-field shielding |
| Ferrite (Mn-Zn) | 1,000–10,000 | 0.4 T | High-frequency (>100 kHz) |
3. Material by Frequency
- DC–100 Hz: Mu-metal, nanocrystalline, silicon steel
- 100 Hz–10 kHz: Nanocrystalline, mu-metal
- 10 kHz–1 MHz: Nanocrystalline, ferrite
- 1 MHz+: Ferrite, copper sheet (eddy current)
4. Design Tips
- Thickness: for low-frequency fields, thickness matters more than permeability
- Enclosure geometry: fully enclosed box is far better than flat sheet; gaps reduce effectiveness
- Multiple layers: inner high-μ layer + outer high-Bsat layer for difficult cases
- Annealing: mu-metal work-hardens when bent—anneal after forming
5. Applications
- MRI room shielding (mu-metal walls)
- Medical device sensor protection
- Audio equipment hum prevention
- Industrial Hall sensor shielding
6. Sirui-Tech Shielding Materials
- Nanocrystalline shielding sheets: flexible, high permeability
- Permalloy alternatives: cost-effective nanocrystalline
- Custom shield shapes: cut and formed to spec
Conclusion
Low-frequency magnetic shielding requires high-permeability materials like mu-metal or nanocrystalline. For high fields, add a high-Bsat outer layer. Fully enclosed geometry is essential. Nanocrystalline increasingly replaces mu-metal for better performance at lower cost.
Need magnetic shielding materials? Contact Sirui-Tech at sales@sirui-tech.com with your field frequency and attenuation requirement.