Abstract:

In this study we investigated the magneto-transport properties of the ohmic contact between polycrystal-line NiMnSb thin films grown by pulsed laser deposition and n-type degenerate InSb (100) substrates. An unusual negative giant magnetoresistance (n-GMR) effect is found when the external magnetic field is parallel to the in-plane current direction. A similar effect is also observed when Ni films are deposited on InSb substrates. On the other hand, no n-GMR effect is displayed when the deposited film is nonmagnetic. Grazing-incidence X-ray reflectometry shows the formation of a low-density NiMnSb layer at the interface. The presence of such a layer coincides with the appearance of the n-GMR. We argue that the n-GMR effect is due to magnetic precipitates formed at the interface during the growth of the magnetic films. We propose that these precipitates align their magnetic moments in the direction of the external magnetic field and thus, the spin dependent scattering of the electrons is reduced. The effect of these precipitates on the magnetoresistance depends on the thermal processing of the system. © 2007 WILEY-VCH Verlag GmbH & Co. KGaA.

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