Perpendicular Hot Electron Spin-Valve Effect in a New Magnetic Field Sensor: The Spin-Valve Transistor

Abstract

A new magnetic field sensor is presented, based on perpendicular hot electron transport in a giant magnetoresistance (Co/Cu)4 multilayer, which serves as a base region of an n-silicon metal-base transistor structure.A 215% change in collector current is found in 500 Oe (77 K), with typical characteristics of the spin-valve effect. The in-plane magnetoresistance was only 3%. The transistor structure allows the investigation of energy resolved perpendicular transport properties, and in particular spin-dependent scattering of hot electrons in transition-metal as well as rare-earth-based multilayers.PACS numbers: 72. 15. Gd, 73.40.Vz, 75.50.Rr, 85.70.Kh The discovery of giant magnetoresistance in magnetic multilayers [1] (also called the spin-valve effect [2]) has led to a large number of studies on giant magnetoresistance systems. Usually, the resistance of the multilayer is measured with the current in plane (CIP). This is the easiest experimental approach of electrical transport in magnetic multilayers. Devices exhibiting CIP giant magnetoresistance are under development as magnetic field sensors, for instance, in read-back magnetic heads used in magnetic recording technology. However, from a fundamental point of view, the CIP configuration suffers from several drawbacks; the CIP magnetoresistance (MR) is diminished by shunting and channeling [2,3].In particular, uncoupled multilayers or sandwiches with thick spacer layers suffer from this problem, whereas the saturation field in such systems is usually small. Moreover, diffusive surface scattering reduces the MR for sandwiches [2] and thin multilayers [4]. Finally, fundamental parameters of the effect, such as the relative contributions of interface and bulk spin-dependent scatterings, are difficult to obtain using the CIP geometry [5]. Measuring with the current perpendicular to the planes (CPP) solves most of these problems, mainly because the electrons cross all magnetic layers, but a practical difficulty is encountered; the perpendicular resistance of the ultrathin multilayers is too small to be measured by ordinary techniques. The first CPP-MR experiments were reported on Co/Ag multilayers [6], where the multilayer was sandwiched between superconducting Nb leads. In this way, CPP experiments could be performed, albeit only at liquid helium temperatures. The use of microfabrication techniques for CPP measurements from 4.2 to 300 K was first shown for Fe/Cr multilayers [7], where the multilayers were etched into micropillars to obtain a relatively large resistance (a few mA). Both types of measurements have confirmed the larger MR effect for the CPP configuration, but they suffered from the general complexity of realization and measurement techniques. Experiments using electrodeposited nanowires showed CPP-MR up to 15% at RT [8].In this Letter, we present the design, prospects, and experimental results of a new magnetic field sensor and measurement tool based on perpendicular hot electron transport in a spin-valve multilayer: the spin-valve transistor. Here...

Riesenmagnetowiderstand — Transfer in die Anwendung

“…rende Prinzipien vorgestellt und im Labor experimentell verifiziert [8]. In diesem Bereich beginnen die Arbeiten derzeit, sich mit konkreteren Anforderungen wie dem Verhaltnis Sperr-zu DurchlaRstrom, der Ansteuercharakteristik oder der Temperaturstabilitat zu befassen.…”

Systematic two-band model calculations of the GMR effect with metallic and non-metallic spacers and with impurities

“…9, for n s = 3 and the parameters (i) and (ii), respectively, our results for the GMR and the conductances are presented over the strength of the disorder, i.e. over the standard deviation σ r in equation (9). For the parameter set (i), Fig.…”

“…there is renewed interest in spin-polarized tunneling through semi-conducting or non-conducting spacers [6,7,8], based on the perspective of new applications in magneto-electronic technology, e.g. for magnetic-field sensors, spin-valve transistors [9] or spin-polarized field-effect transistors [10,11].…”

Calculations of hot electron magnetotransport in a spin-valve transistor at finite temperatures

“…For instance, magnetic tunneling junction (MTJ) [2] has been explored very actively for real device applications. Interestingly, Monsma et al presented a spin-valve transistor [3] as a new type of magnetoelectronic device.…”