GB1112835A

GB1112835A -

Info

Publication number: GB1112835A
Authority: GB

Abstract

1,112,835. Semi-conductor devices. SIEMENS A.G. 28 March, 1967 [29 March, 1966], No. 14181/67. Heading H1K. [Also in Division H2] A magneto-resistive arrangement is provided with a magnetic circuit including a permanent magnet portion of low permeability and high coercivity relative to the rest of the circuit, and means for applying a variable magnetic field to the arrangement. As shown, Fig. la, a magneto-resistive element or field plate 1 together with a ferrite carrier body 2 is mounted between a pair of ferromagnetic plates 4, 5 by means of which the flux B o due to a permanent magnet 3 and also a variable external flux B a are applied to the field plate. The magnet has the characteristics described above to ensure that the external flux passes through the field plate rather than through the magnet. The magnet may be of an oxidic material having a permeability of approximately 1. Modifications are described with reference to Figs. 1b and 1c (not shown) in which the field plate is mounted between a pair of ferrite bodies, or between a pair of iron bodies with interposed insulation, respectively. Application of an external magnetic field of less than 1 kg. does not affect the working point of the arrangement, but higher fields change the field due to the permanent magnet causing a shift in the working point on the characteristic curve. The arrangement may be used as a contactless transducer, Fig. 3 (not shown), by arranging a magnet so that its movements cause a varying flux to be applied to the device. A plurality of the arrangements may be used to form a contact-less commutator for a D.C. motor having a permanent magnet rotor, each of the arrangements controlling the current in a field coil by means of a transistor amplifier, Figs. 4 and 5 (not shown). The field plate may be of an A<SP>III </SP>B<SP>v</SP> compound such as indium antimonide or indium arsenide, and may contain aligned inclusions of a second material of good conductivity, for example, needles of nickel antimonide in indium antimonide.