Microscale sintered magnets for MEMS type applications

Abstract

Magnetic micro-actuators and systems require tiny permanent magnets with dimensions of hundreds of micrometres. Such magnets need to have the highest possible energy density, which means Nd–Fe–B is the most appropriate material. Most bottom-up fabrication techniques are either too slow or too expensive; top-down techniques involving machining tend to result in surface damage and a loss of magnetic properties. Thus, PM is an attractive route. It is shown that use of very neodymium-rich Nd–Fe–B powders makes it possible to sinter 100 μm thick specimens to full density at temperatures as low as 800°C. These very thin magnets have coercivities of up to 1000 kA m⁻¹ and are suitable for micro-actuator type applications.