Abstract
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Of the perovskites, ABX3, a subset of special interest is the family in which the A site is
occupied by a lanthanide ion, the B site by a transition metal and X is oxygen, as such
materials often exhibit a large change in electrical resistance in a magnetic field, a
phenomenon known as "colossal" magnetoresistance (MR). Two additional phenomena in
this family have also drawn attention: the metal-insulator transition (MIT) and
electroresistance (ER). The MIT is revealed by measuring resistance as a function of
temperature, and observing a change in the sign of the gradient. ER – the dependence of
the resistance on applied current – is revealed by measuring resistance as a function of
applied current. Up until now, the phenomena of MIT and ER have been treated separately.
Here we report simultaneous observation of the MIT and ER in the lanthanum/calcium
manganites. We accomplish this by measuring voltage-current curves over a wide
temperature range (10–300 K) allowing us to build up an experimental voltage surface
over current-temperature axes. These data directly lead to resistance surfaces. This
approach provides additional insight into the phenomena of electrical transport in the
lanthanum/calcium manganites, in particular the close connection of the maximum ER to
the occurrence of the MIT in those cases of a paramagnetic insulator (PMI) to
ferromagnetic metal (FMM) transition.
PACS Codes: 71.30.+h, 71.38.-k, 75.47.Lx