Ask most developers about magnetic sensors and they’ll first think of the Hall Effect. But there’s another approach that has come to market, one that promises increased sensitivity, smaller sensor size, and lower power consumption. Leveraging the quantum effect of magnetic junction tunneling (MJT), Crocus Technology is poised to deliver next-generation magnetic sensors, switches, and memory technology.
A Hall Effect sensor works on the principle that a magnetic field will deflect moving electrons. That deflection results in a voltage difference across the sensor at right angles to the current flow. The MJT sensor uses quantum tunneling through a thin insulating layer between magnetic electrodes, one of which has a fixed magnetization and the other of which can follow an applied field. The probability of tunneling (acting, in effect, like resistance) depends on the relative orientation of the two fields. This dependency allows the MJT cell to act as a field strength sensor or as a switch.
According to Michel Desbard, CEO of Crocus Technology, the MJT sensor is orders of magnitude more sensitive than traditional Hall Effect sensors. “A Hall Effect switch needs the gap between it and the magnet to be a millimeter or less,” said Desbard in an interview with EE Times. “Our sensors can be inches away.”
Desbard also pointed to several other advantages of the MJT sensor. “With Hall Effect you get microampers or microvolts of signal, which need to be amplified. Our sensor generates millivolts, which can feed an MCU directly.” Sensors can also be 100x smaller than Hall Effect equivalents, Desbard said, operate at temperatures to 250°C, and can be readily integrated with logic to form single-chip sensors. “The sensor materials can be deposited onto any CMOS technology,” which also makes them less expensive to produce, Desbard noted.