Introduction to TMR Magnetic Sensors

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Introduction to TMR Magnetic Sensors
Magnetic transducers are widely used in modern industry and electronics to sense the magnetic field strength to measure current, position, motion, direction, and other physical parameters. In the technical field of magnetoresistive transducers, there are many different types of sensors for measuring magnetic field and other parameters. Commercially important ones, in order of technical advancement, include: Hall Effect, Anisotropic MagnetoResistance (AMR), Giant MagnetoResistance (GMR), and the latest:Tunneling MagnetoResistance (TMR).

The Hall element is a magnetic sensor sensing element for which the applied magnetic field is typically amplified using magnetic flux concentrator to improve the sensitivity of the Hall output, thereby increasing the size and weight of the sensor. Hall elements have large power consumption and poor non-linearity. The AMR element has much higher sensitivity than the Hall element, but it has a narrow linear operating range.  The AMR magnetic sensor sensing elements need to use a set / reset coil for their preset / reset operation. This results in increasing the complexity of their manufacturing process, while also increasing their size and power consumption. The GMR magnetic sensing element sensitivity is higher than for AMR, but its linear range is still low.

Recently, TMR (Tunnel MagnetoResistance) elements were introduced as a new type of magnetoresistance sensor for industrial applications. They are constructed as a magnetic multilayer film material.  TMR magnetic field sensing elements exhibit a greater change in resistivity, as a function of applied magnetic field induction, than that of the previously developed magnetoresistance technologies, AMR and GMR.  The term Magnetic Tunnel Junction (MTJ) is used to refer to a TMR sensing element.

Relative to a Hall effect element, an MTJ element has better temperature stability, higher sensitivity, lower power consumption, better linearity, and needs no additional flux concentrator structure. Relative to an AMR element, an MTJ element has better temperature stability, higher sensitivity, wider linear range, and needs no set / reset coil. Relative to a GMR sensing element, an MTJ has better temperature stability, higher sensitivity, lower power consumption, and a wider linear range.

MultiDimension Technology (MDT®) was founded in 2010 in Zhangjiagang, Jiangsu Province, China, with branch offices in Ningbo, Shanghai, Chengdu, China and San Jose, Calif., USA. MDT has developed an unique intellectual property portfolio, and state-of-the-art manufacturing capabilities that can support volume production of high-performance, low-cost TMR magnetic sensors to satisfy the most demanding application needs. Led by its core management team of experts in magnetic sensor technology and engineering services, MDT is committed to creating added value for its customers and ensuring their success.

MDT’s service options include:

  • In-plane and Z-axis TMR sensors, which may be delivered as wafers, bare dice, or packaged devices
  • Custom design for TMR/GMR/AMR sensors
  • ASIC design for integration with TMR/GMR/AMR sensors
  • Foundry service for TMR/GMR/AMR sensors including thin-film deposition, device processing, packaging and testing
  • Custom sensor module design and application solutions
  • IP licensing, granting customers access to MDT ’s technology for use in their products