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Hamburg 2001 – wissenschaftliches Programm

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AM: Magnetismus

AM 3: Magnetowiderstand I

AM 3.14: Vortrag

Montag, 26. März 2001, 17:45–18:00, S 5.2

Effect of Spin Polarized Tunneling in Transport properties of CMR Manganites — •Chiranjib Mitra1,2, Kathrin Dörr2, and Karl-Hartmut Müller21TIFR , Homi Bhabha Road, Colaba, Mumbai 400 005, India — 2IFW Dresden, Postfach 270116, 01171 Dresden, Germany

La0.7Ca0.3MnO3 and La0.7Sr0.3MnO3 are perovskites manganites exhibiting colossal magnetoresistance (CMR) at the ferromagnetic ordering temperature, where upon application of large magnetic fields (∼ Tesla) the spin disorder resistivity is suppressed giving rise to an enormous MR near TC. These systems behave as half metallic ferromagnets and this produces a low field MR below TC in polycrystalline films and granular materials owing to the spin polarized tunneling (SPT) of the heavily polarized conduction electrons across the grain boundaries which act as insulating barriers. In this work we have investigated the effect of SPT across artificially fabricated tunnel junction in CMR-Insulator-CMR multilayers. From our current perpendicular to plane (CPP) transport data we have observed a very intriguing temperature dependence of MR, which is attributed to arising from the temperature dependent evolution of density of states (DOS) in manganites below TC owing to the large Hund’s coupling. We also observe a gradual suppression of Jahn-Teller polarons with decrease in temperature below TC in our tunneling resistance data.

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