Measuring magnetoelectric and magnetopiezoelectric effects

The authors have developed a test procedure and circuits for characterizing the charge generation of a magnetoelectric device when stimulated with a magnetic field. The magnetoelectric effect comes in two physical forms. The first is from a ferroic material such as Bismuth Iron Oxide (BFO) which exhibits internal coupling between its magnetic properties and its ferroelectric properties. The second is from composite devices which are constructed by mechanically coupling a magnetic material to a piezoelectric material. A magnetic field applied to a composite device creates stress in the magnetic material which transfers the stress to the piezoelectric material. The traditional method for measuring magnetoelectric effect is to stimulate the sample with a magnetic field while measuring the voltage generated across the sample. These voltages can be so small that a lock-in amplifier is required to pull the signal out of ambient noise. Charge measurement under the same circumstances produces a much larger signal and can be related to the voltage response using the dielectric constant of the material [1]. The charge test is an exact analog to the traditional electrical hysteresis test with the exception that the test instrument applies a magnetic field to the sample instead of an electric field. The presenter will describe the test procedure as presently used and outline future objectives for improving the accuracy and sensitivity of the results.