Magnetoreactive element and new solid-state inductor

Abstract

Theoretical and experimental investigations have been made on the characteristics of impedance variation of an intermetallic semiconductor element under a magnetic field. It has been known that the resistance across the current terminals of a Hall element increases under a magnetic field if the Hall terminals are short-circuited because the transverse Hall current produces a secondary Hall voltage across the current terminals resulting in the increase of the voltage. When an external reactance, L or C is connected to the Hall terminals, the other type of reactance, C or L, appears across the current terminals, since the Hall current becomes out of phase with the element current. This is the principle of a magnetoreactive element. Under a fixed magnetic field, the increase in impedance of the element makes a circular locus in a complex plane, when the external reactance across the Hall terminals is varied. The maximum reactance is obtainable when the external reactance is equal to the internal resistance between the Hall terminals. One of the interesting features of the device is that the sign of the induced reactance is opposite to that of the one connected across the Hall terminals. Thus an inductance can easily be obtained with a structure for capacitance. With a fixed external reactance, the induced reactance of the element increases with the magnetic field, though the resistance also does owing to the magnetoresistance effect. Accordingly, the ratio of the reactance, which becomes maximum under a certain magnetic field, is one of the figures of merit. Experimental results with a high purity InSb element agreed very well with theoretical calculations. It is suggested that this kind of element may be used as a variable reactance or impedance device as well as a solid-state inductor. Special types of construction have been developed for this purpose. An element of p- d- n sandwich structure shows an inductance of some several hundred μH at 10 kG at 77°K.