GB1413431A - Solid-state switching systems - Google Patents

Abstract

1413431 Semi-conductor switching SIEMENS AG 28 March 1973 [30 March 1972] 14411/73 Heading H1K A solid state switching system comprises a body of magnetic s/c material with electrodes thereon, connected to a voltage source; with means for applying a variable strength magnetic field of preselected direction; wherein the body is held at a temperature not exceeding the Curie point of the material and within the zone of critical fluctuation of the spin system; and switching from a high ohmic to a low ohmic state is effected by increasing the magnetic field strength and vice versa by decreasing it; the electrode voltage producing an electric field, of itself ineffective to switch the body but effective to reduce the necessary strength of the magnetic field and/or the necessary strength variation for switching as compared with the strength or variation necessary in the absence of such electric field. The semi-conductor material may be crystalline or amorphous; ferromagnetic, ferromagnetic or metamagnetic; for example chalcogenides and/or halides. It may be a compound of the type AB 2 X 4 where A is at least one of the elements Eu, Sr, Ba, Pb, Zn, Cd, Hg, Mg, Mn, Co; B is Cr, or Rh; X is S or Se. The oxides, sulphides, selenides or tellurides of Sa, Eu, Yt are also usable, as are Cd-Zn-Ga-Cr sulphide or selenide, Fe-Cd-Ag-Cr sulphide or selenide. The magnetic semi-conductor may also comprise a compound of at least one of the elements Eu, Sr, Ba, Pb, with at least one of the elements Cu, Ag, Au, Li, K, Na, Zn, Cd, Hg, Sn, Pb or at least one of the elements Lu, Y, Sc or at least one of the elements V, Mn, Fe, Co, Ni, B, Al, Ga, In, Tl and with at least one of the elements Cl, Br, I and at least one of the elements S, Se, Te. The semi-conductor element may also be of Ag or Cu doped Eu-Cr selenides. Constructionally the switching element has flat electrodes forming ohmic contacts on opposed faces and is subjected to magnetic fields axial or normal thereof, or a superimposed combination of such fields; the electrodes being energized from a voltage source over a series resistor. Specifically the switching element 71 (Fig. 2) has an area 41 of its surface forming a PN junction derived from appropriate choice of electrode material so that electrode 16 forms an ohmic junction and electrode 141 a unidirectional PN junction with the element. The electrode materials may be Cu, Ag, Au, Pt, Rh, Cr, Mo, Al, Ga, In, Pb, Zn, Cd, Hg or binary alloys thereof, and the switching characteristics of current as ordinate 20 and voltage as abscissa 21 are shown (Fig. 3) at 22 and 23 for low ohmic and high ohmic states, wherein the applied magnetic field flux densities are zero and IVs./m.<SP>2</SP> respectively, and a series resistor 125 is included to limit the low ohmic current. At transition the voltage source 25 is switched off momentarily to erase the low ohmic state.