# Current switching in semiconducting $LaMn_{1-x}MgxO_{3+\delta^{-}}$

Philip, J and Kutty, TRN (2002) Current switching in semiconducting $LaMn_{1-x}MgxO_{3+\delta^{-}}$. In: Materials Chemistry and Physics, 73 (2-3). pp. 220-226.

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Official URL: http://dx.doi.org/10.1016/S0254-0584(01)00381-9

## Abstract

The semiconducting LaMn1-xMgxO3+delta (LMMO) exhibits highly nonlinear, voltage-limiting, conduction (current switching) in the current-voltage (J-E) relationship. The nonlinearity is observed at field strengths less than 50 V/cm and below the magnetic transition temperature (T-c). The current density in the conducting region is very high, reaching tens of A/cm(2). The threshold electric field (E-TH) shifts to lower values in presence of an external magnetic field. No current switching is observed in ferromagnetic metallic, La0.67Ca0.33MnO3+delta (LCMO) specimens. The nonlinearity observed in LMMO cannot be explained on the basis of antiferromagnetic/paramagnetic insulating phases co-existing with ferromagnetic metallic phases below T-c, because such giant clusters are observed in LCMO. Substitution of Mg increases the Mn4+ concentration, however, does not induce a transition to metallic state below T-c even at high hole concentration; instead, displays the behaviour of localisation. Localisation of carriers is due to the increased hole hopping distance (Mn3+-O-Mg2+-O-Mn4+) and by the spin canting. Below T-c, in the canted ferromagnetic state, the carriers can be delocalised by applying an electric field. The electric field enhances the mobility of the carriers and increases the hopping probability. Above E-TH, large number of carriers are delocalised and set in for conduction, yielding high current density.

Item Type: Journal Article Copyright of this article belongs to Elsevier Science . Colossal Magnetoresistance;Transport-Properties;Doped Manganites;Lamno3+Delta;Perovskites Division of Chemical Sciences > Materials Research Centre 01 Jun 2009 05:55 29 Jun 2011 12:19 http://eprints.iisc.ernet.in/id/eprint/17730