Ian Walker of GMW Associates will review the development of projected-field electromagnets for device testing.

Wednesday Mar 11, 2026 6:30–8:00 PM PT Hybrid Meeting Online or at Quadrant San Jose, CA REGISTER as a Guest or as an IEEE member

During early development of MRAM devices, there was a need to apply controllable magnetic fields to devices under test while maintaining compatibility with conventional wafer probers and optical alignment systems. Traditional dipole electromagnets with large pole gaps were poorly suited to this task due to their size, mechanical constraints, and limited accessibility. Recognizing that the functional region of interest for many devices is effectively localized to a point, an alternative approach was developed that exploits the fringe field of a compact electromagnet positioned near the device.

In this approach, the electromagnet is mechanically decoupled from the probing system and can be moved into position only during magnetic-field-dependent electrical measurements, allowing unobstructed alignment and probing. Although the resulting field is inherently non-uniform, it is well controlled at the device location, making it suitable for a wide range of device characterization tasks. The term “Projected Field Electromagnet” has been adopted to describe this class of field sources, emphasizing the delivery of a defined magnetic field to a specific spatial location rather than the creation of a large uniform field volume.

This concept has since been extended to support in-plane, vertical, and three-component magnetic field configurations, as well as both DC and low-frequency AC operation. Variations of the design address different trade-offs between field amplitude, spatial uniformity, working distance, and mechanical accessibility. An example extension includes a vertical-field configuration that provides a modestly uniform field region at a defined distance from the magnet surface. The talk will focus on the underlying design principles, practical implementation considerations, and application examples relevant to device-level magnetic testing.

Agenda:

Speaker:

Ian Walker, Cofounder and Applications Engineer, GMW Associates, was initially involved in designing electromagnet systems for ion beam control of ion implanters for semiconductor doping. The Ion Implantation Group later split off as Zimec, and Ian became President of GMW, specializing in electromagnet systems for materials and physics studies and in sensors for magnetic field and magnetically isolated electric current measurements. Several years ago, Brian Richter became President of GMW, and Ian has since led the more relaxed life of an Applications Engineer.