Attach an NFC tag to a metal water bottle and bring the phone close - there is no response. This is not because the label is broken, but because the metal has' eaten 'the signal.

The operating frequency of NFC and most high-frequency RFID is 13.56MHz, and communication relies on the alternating magnetic field generated by antenna coils. When this alternating magnetic field encounters a metal surface, according to Faraday's law of electromagnetic induction, eddy currents will be generated in the metal. The direction of the eddy current is opposite to the original magnetic field of the antenna, forming a counteracting reverse magnetic field that weakens or even completely cancels out the effective signal of the antenna. The result is a sharp reduction in read-write distance and communication failure.

2、 Focused magnetic flux and low magnetic loss: a pair of parameters that require precise balance

The core function of 13.56MHz absorbing materials is determined by two key parameters: the real part of magnetic permeability (μ ') and the imaginary part of magnetic permeability (μ'), as well as the loss tangent tan δ (=μ '/μ') defined by the ratio of the two.

The Way of Balance:μ 'determines' how much magnetic flux can be bundled', and tan δ determines' whether the bundled signal is interference or useful '. The ideal 13.56MHz absorbing wave plate needs to have a sufficiently high μ 'to resist metals and a sufficiently low tan δ to avoid loss of useful signals. Generally, when the magnetic permeability of absorbing materials is above 10MHz, μ 'rapidly decays and μ' rapidly increases. Therefore, 13.56MHz is the critical frequency point for high-frequency anti metal applications.

3、 Ferrite vs nanocrystals: material system selection

4、 Key Performance: What Engineers Should Pay Attention to

5、 Typical application scenarios

6、 Selection considerations: from thickness to magnetic permeability

7、 Conclusion

The essence of 13.56MHz absorbing materials is to use high magnetic permeability materials to "build a path around the metal" for the magnetic field lines of NFC/RFID. It does not change the communication protocol or amplify signal power - it only changes the spatial distribution of magnetic field lines, allowing the magnetic field that should have been "short circuited" by the metal to return to the effective area of the antenna.

Understanding the working logic of absorbing materials - focusing magnetic flux instead of amplifying signals, low magnetic loss instead of high loss - is the key to upgrading this thin film with a thickness of less than 0.1mm from an "accessory" to an "engineering solution". In scenarios such as metal body phones, metal surface labels, and industrial metal environments, the 13.56MHz absorbing material provides the final piece of the puzzle for near-field communication to move from "ideal laboratory conditions" to the "real engineering world".