Metal-insulator transition and electroresistance in Ianthanum/calcium manganites La1-xCaxMn03 (x=0-0.5) from voltage-current-temperature surfaces

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