A group of Chinese scientists has developed a Hall-effect magnetic sensor — based on the physical phenomenon that occurs when an electric current passes through a material placed under the influence of a magnetic field — that combines microscopic dimensions, high sensitivity and low noise levels, opening the way for applications ranging from medicine and industry to, in the future, submarine detection.
The device was developed by a team at the Chinese Academy of Sciences (CAS) and features a detection area of just 20 by 20 micrometres. According to the researchers, the technology is capable of detecting extremely weak magnetic fields, a capability that could allow it to identify changes produced by moving metallic objects.
Hall-effect sensors are already used in a range of electronic equipment, including smartphones, smartwatches, automotive speed sensors and medical devices. They operate by generating a small electric voltage in the presence of a magnetic field. The principal challenge facing these sensors is noise. 'The smaller and more sensitive they are, the greater the interference tends to be from the magnetic material itself, making it difficult to detect very weak signals,' the team noted.
The Chinese team found that this noise is linked to the movement speed of so-called spin textures — microscopic patterns formed by the behaviour of electrons in magnetic materials. The faster these structures move, the lower the noise produced. Building on this discovery, the scientists developed an artificial ferromagnetic structure capable of accelerating the dynamics of these textures, achieved by carefully adjusting the thickness of the different magnetic layers and the material's heat treatment process.
The result was an anomalous Hall-effect magnetic sensor with an extremely small area and high sensitivity. One of the possibilities attracting the most attention is the use of the technology in submarine detection. A steel-hulled submarine moving through the Earth's natural magnetic field causes small disturbances in that field. Sufficiently sensitive sensors can detect these anomalies through a technique known as magnetic anomaly detection, or MAD.
In practice, however, the technology is still far from enabling the detection of submarines at long range. The sensitivity achieved in the study may allow for detection of a submarine at a relatively short distance, but further advances are needed before the technology can be applied to long-range military applications.
The technology could also find applications in the automotive industry, electronic component manufacturing and materials science. One possibility is the use of the sensors in scanning probe microscopy, enabling the observation of magnetic properties of materials at the microscopic scale. The researchers believe the principle used in developing the sensor could be applied to other magnetic materials, some of which may exhibit even faster spin dynamics, reducing noise and significantly increasing sensor sensitivity in the future.
Source: Diário Económico
Original article: https://www.diarioeconomico.co.mz/?p=530986
