Magnetic materials are those that distort magnetic flux lines. Some materials do this because they have high magnetic conductivity, while others, such as magnetite, have magnetic fields all of their own.
Magnetism varies from place to place. This variation is caused by the different nature and composition of rocks, for example, or the interaction between the magnetosphere (the region of Earth’s magnetic influence) and charged particles from the sun.
A magnetometer is a scientific instrument used to measure the strength and/or direction of magnetic fields, as well as their orientation and direction.
Over and above the more well-known and “traditional” uses of magnetometers – metal detectors, locating submarines and shipwrecks, compasses etc. – there are many other fascinating applications for these amazing instruments.
Our hearts and brains generate their own magnetic fields. An amazing piece of equipment known as a superconducting quantum interference device (SQUID) is a magnetometer used to detect and measure the magnetic fields generated by electric current. Used in conjunction with an MRI machine, doctors can use the SQUID to transpose magnetic field signals over specific areas of the brain, helping them to diagnose epilepsy and Alzheimer’s.
SQUID magnetometers are also used to detect depolarization and repolarization of heart muscle, and can diagnose and treat dysrhythmias, which can be potentially life threatening. The same magnetometer is used by obstetricians to assess fetal heart conditions, and by specialists to diagnose gastroenterological disorders.
Smartphones, Tablets and PCs
Over half a billion magnetic compass sensors for mobile phones were sold in 2013 – compared to 8.7 million in 2008. A navigation function is fast becoming the latest have-to-have feature on smartphones, with users wanting, indeed expecting, their phones to be able to give them turn-by-turn directions. This function, combined with the compasses that many phone already have, will herald the beginning of location-based augmented reality – where a street map is overlaid with highly detailed information about what your phone “sees” in front of it.
A three-axis magnetometer will help make these expectations a reality, homing in on Earth’s magnetic field and using that to determine the handset’s orientation. Three axes mean users can hold the phone naturally, instead of precisely parallel to the ground as would happen with a two-axis sensor.