Magnetic Sensors Based on Amorphous Ferromagnetic Materials: A Review

Abstract

Currently there are many types of sensors that are used in lots of applications. Among these, magnetic sensors are a good alternative for the detection and measurement of different phenomena because they are a “simple” and readily available technology. For the construction of such devices there are many magnetic materials available, although amorphous ferromagnetic materials are the most suitable. The existence in the market of these materials allows the production of different kinds of sensors, without requiring expensive manufacture investments for the magnetic cores. Furthermore, these are not fragile materials that require special care, favouring the construction of solid and reliable devices. Another important feature is that these sensors can be developed without electric contact between the measuring device and the sensor, making them especially fit for use in harsh environments. In this review we will look at the main types of developed magnetic sensors. This work presents the state of the art of magnetic sensors based on amorphous ferromagnetic materials used in modern technology: security devices, weapon detection, magnetic maps, car industry, credit cards, etc.

Ultrathin Nanocrystalline Magnetic Wires

“…Long cylindrical ferromagnetic wires with excellent soft magnetic properties [1,2] have been of interest for numerous applications, mainly in sensing devices such as electrical current and magnetic field sensors aimed for medical and automotive uses [3][4][5]. To obtain a low coercivity, H C , accompanied by a high relative magnetic permeability, µ r , such materials have been produced mainly in amorphous state, in order to avoid any magnetocrystalline anisotropy.…”

Highly Sensitive Flexible Magnetic Sensor Based on Anisotropic Magnetoresistance Effect

“…The AMR effect is based on the anisotropic scattering of conductive electrons with uncompensated spins. With a positive AMR coefficient, the resistance of Permalloy (Py: Ni 0.81 Fe 0.19 ) is at maximum when magnetization M and current density J are parallel ( R // ) and is at minimum when M and J are perpendicular with each other ( R ⊥ ) . The resistance can be expressed as where ΔR = R // − R ⊥ , H ext < H 0 , H 0 is the total magnetic anisotropy field, and H ext is the external magnetic field perpendicular to the easy axis.…”

Reconfigurable Magnetoresistive Sensor Based on Magnetoelectric Coupling

“…In the ferromagnetic thin films, the AMR effect is usually treated as a 2D problem. The resistance R depends on the angle φ between the magnetization M and the current I 44 where R p for M parallel with I , and R o for M orthogonal with I .…”

“…The resistance R depends on the angle ϕ between the magnetization M and the current I. [44] ( ) ( )cos c os…”