Journal of Magnetism and Magnetic Materials 214 (2000) L1}L6 Letter to the editor Low-"eld magnetocurrent above 200% in a spin-valve transistor at room temperature P.S. Anil Kumar*, R. Jansen, O.M.J. van 't Erve, R. Vlutters, P. de Haan, J.C. Lodder Information Storage Technology Group, MESA Research Institute, University of Twente, 7500 AE, Enschede, Netherlands Received 9 February 2000 Abstract A spin-valve transistor (SVT) that employs hot electrons is shown to exhibit a huge magnetotransport e!ect at room temperature in small magnetic "elds. The SVT is a ferromagnet-semiconductor hybrid structure in which hot electrons are injected into a NiFe/Au/Co spin valve, and collected on the other side with energy and momentum selection. This makes the collector current extremely sensitive to spin-dependent scattering. The hot-electron current output of the device changes by more than a factor of three in magnetic "elds of only a few Oe, corresponding to a magnetocurrent above 200% at room temperature.  2000 Elsevier Science B.V. All rights reserved. PACS: 85.70.Kh; 73.50.!h; 73.40.!c Keywords: Hot electron; Spin valve; Magnetotransport; Schottky barrier The discovery of giant magnetoresistance (GMR) in metallic multilayers [1,2] composed of alternating ferromagnetic (F) and non-magnetic (N) layers has triggered intense investigation because of its scienti"c as well as technological importance. In GMR multilayers, the scattering of electrons at the F/N interfaces and/or within the F layers is spin- dependent. This causes the overall resistance to depend on the relative orientation of the magneti- zation of successive F layers, which can be control- led by an external magnetic "eld. The search for novel magnetotransport devices is being pursued as they exhibit fascinating new phys- ical phenomena and can potentially be used [3] as * Corresponding author. Fax: #31-53-489-3343. E-mail address: p.s.a.kumar@utwente.nl (P.S. Anil Kumar). magnetic read heads, magnetic "eld sensors and nonvolatile memory elements in magnetic random access memories (MRAM). High sensitivity at low applied magnetic "eld and room-temperature op- eration are parameters of importance. The GMR systems such as Co/Cu and Py/Cu multilayers, etc. (Py"Ni  Fe  ) have been extensively studied in this regard [4,5]. However, the relative sensitivity in these systems are much smaller than that of Py "lm exhibiting anisotropic magnetoresistance 4% per Oe [6]. A modi"ed structure containing two di!erent ferromagnetic layers which are exchange decoupled by a spacer metallic layer is introduced to obtain better magnetoresistance (R/R&14%) at low "elds, e.g. Py/Cu/Co system [7,8]. A change in measuring geometry from current in plane (CIP) to current perpendicular to the plane (CPP) gives LETTER TO THE EDITOR 0304-8853/00/$ - see front matter  2000 Elsevier Science B.V. All rights reserved. PII: S 0 3 0 4 - 8 8 5 3 ( 0 0 ) 0 0 0 5 2 - 4