National Physical Laboratory

Electromagnetic Materials

Magnetic and Dielectric Measurements

Electromagnetic (EM) industries rely heavily upon high performance materials that are designed to support, direct, condition or absorb EM fields. In a wide range of applications EM fields also come into contact with other natural substances, for example: earth, water, and biological tissues. Full characterization of all of these material interactions is essential for optimal design of instrumentation. This can only be achieved with a knowledge of the intrinsic dielectric and magnetic properties of the materials involved: typically their complex dielectric permittivity and magnetic permeability, but also related parameters such as anisotropy, susceptibility and coercivity. NPL has a long history of successful EM material metrology and is actively developing its capabilities here to ensure that they meet the requirements of modern technology. Measurement research is being tackled on a broad front:

  • Provision of materials measurement solutions in key bands across the whole spectrum: DC, LF, RF, microwave, THz and above. Special measurement techniques are being developed for active functional materials, including piezoelectric, ferroelectric and multiferroic materials.
  • Measurements are required at ever smaller scales to allow faster, lighter, more compact and more energy efficient solutions to be developed in the electronics industries: traceable methods for probing of EM material properties at micro to nano-scales are being developed to meet this need and to characterise the properties of thin films.
  • There are growing requirements for measurements to be undertaken in situ in harsh environments: for example high temperature and high pressure measurements on magnetic materials are needed to improve electrical power generation and similar measurements on dielectric materials are required to improve efficacy of microwave processing.
  • Public concern over increasing exposure to broadcast RF and microwave signals has prompted widespread research and a requirement for traceable standards to quantify exposure. NPL has an ongoing research activity in this field. Dielectric measurement solutions are essential here as human tissues have their own dielectric response to EM fields.

Electromagnetic Materials products and services

  • NPL offers and recalibrates AC conductivity standards covering the range 3 to 103 %IACS (International Annealed Copper Scale) at frequencies from 10 to 100 kHz.
  • Magnetic measurements can be carried out at NPL on a wide variety of magnetic instruments and materials.