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Magnetic field sensors using the magnetoresistive effect

1986; Elsevier BV; Volume: 10; Issue: 1-2 Linguagem: Inglês

10.1016/0250-6874(86)80038-5

1873-3050

U. Dibbern,

Characterization and Applications of Magnetic Nanoparticles

The paper deals with sensors made of ferromagnetic thin films. Either a resistance variation or a voltage (planar Hall efect) caused by a magnetic field is the physical quantity utilized. These sensors can measure fields of less than 10−3 A/m up to several 104 A/m, i.e., much lower fields than normal Hall sensors. The relation between magnetic field and resistance variations is described first and conditions are given to achieve reliable operation even though the magnetic layers show more imperfections. Further sections deal with linearization of the square characteristic and the design of several sensor types. Different materials are compared and the most important manufacturing steps with process data are explained. Applications cover measurement of the (d.c.) field and its variations to reading of magnetically-stored information with signals in the kHz and MHz range. A second area is position sensing with the aid of a permanent magnet; this comprises analog measurement of displacement or angle as well as digital operation by counting the cogs of a gear wheel.