FAQs

The high permeability of Eagle AAA provides a low reluctance path for magnetic flux, leading to its major use, in magnetic shields against static or slowly varying magnetic fields. Magnetic shielding made with high permeability alloys like Eagle AAA works not by blocking magnetic fields but by shunting them—providing a path for the magnetic field lines around the shielded area. So, the best shape for shields is a closed container surrounding the shielded space. The effectiveness of the shielding decreases with the alloy’s permeability, which drops off at both low field strengths and, due to saturation, at high field strengths. So, Eagle AAA shields are often made of several enclosures one inside the other, each of which successively reduces the field inside it. RF magnetic fields above about 100 kHz can be shielded by Faraday shields, ordinary conductive metal sheets or screens which are used to shield against electric fields.

Magnetic shielding was developed by scientists named Smith and Garnett and patented in 1923 for inductive loading of submarine telegraph cables by The Telegraph Construction and Maintenance Co. Ltd. (now Telcon Metals Ltd.), a British firm which built the Atlantic undersea telegraph cables. The conductive seawater surrounding an undersea cable added a great deal of capacitance to the cable, limiting the bandwidth and slowing signaling speed to 10 – 12 words per minute. The bandwidth could be increased by adding inductance to compensate. This was first done by wrapping the conductors with a helical wrapping of metal tape or wire of high magnetic permeability, which confined the magnetic field. Magnetic shielding was invented by adding copper to the previous high permeability alloy Permalloy to improve ductility. Fifty miles of fine shielding wire was needed for each mile of cable, creating a great demand for the alloy. The first year of production Telcon was making 30 tons per week. In the 1930s this use declined, but by World War II many other uses were found in the electronics industry (particularly shielding for transformers and cathode ray tubes) as well as the fuses inside magnetic mines.

Eagle AAA is a nickel-iron alloy (approximately 80% nickel, 15% iron, and molybdenum) that has very high magnetic permeability. The high permeability makes Eagle AAA very effective at screening static or low-frequency magnetic fields, which cannot be attenuated by other methods. Eagle AAA can have relative permeabilities of 80,000-100,000 compared to several thousand for ordinary steel. In addition, it has low coercivity and magnetostriction resulting in low hysteresis loss. Its magnetic properties are similar to other high permeability alloys such as Permalloy, but it is more ductile and workable.

Annealing is an important part of making a nickel shield effective after fabrication and is required. We offer standard vacuum cycle, standard H2 cycle, and customized versions of both.

Eagle AAA meets Mil-N-14411C Comp 1 & ASTM A753-08 Alloy 4. (Updated 2013)

The cost of magnetic shielding depends on several key factors. These include the required level of magnetic field attenuation, the physical size and complexity of the area or device needing shielding, the specific type of shielding material selected for the application, and any custom fabrication or installation requirements.

Selecting the right magnetic shielding material is crucial for achieving the desired level of field attenuation. The ideal material depends on the characteristics of the magnetic field you are trying to shield against, including its strength (DC or AC) and frequency. For low-frequency AC and DC fields, high-permeability alloys are often the preferred choice due to their ability to readily absorb and redirect magnetic flux. In situations involving strong DC fields, iron alloys may be more suitable. Factors like the required level of shielding effectiveness, any weight or size limitations of your application, and the environmental conditions in which the shield will operate also play a significant role in material selection.

Eagle Magnetic brings over 5 decades of experience and expertise. We offer a comprehensive portfolio of high-performance shielding materials, coupled with a wide array of custom fabrication capabilities to meet diverse application needs. Our team of engineers provides dedicated support throughout the entire process, from initial consultation and design to prototyping and final production. We are committed to maintaining the highest standards of quality, so you can trust our products.