A large electric-pulse-induced reversible resistance change active at room temperature and under zero magnetic field has been discovered in colossal magnetoresistive (CMR) Pr0.7Ca0.3MnO3 thin films. Electric field-direction-dependent resistance changes of more than 1700% were observed under applied pulses of ∼100 ns duration and as low as ±5 V magnitude. The resistance changes were cumulative with pulse number, were reversible and nonvolatile. This electrically induced effect, observed in CMR materials at room temperature has both the benefit of a discovery in materials properties and the promise of applications for thin film manganites in the electronics arena including high-density nonvolatile memory.

Recent research on the resistance switching effect in manganite oxide based electric-pulse-induced resistance (EPIR) devices is being reviewed. The EPIR effect encompasses the reversible change of resistance of a thin oxide film such as Pr 1-x Ca x MnO 3 (PCMO) under the application of short, low voltage pulses. Two groups of EPIR devices have been investigated: one with the PCMO layer sandwiched between a top and a bottom electrode; the other with both electrodes on top of the PCMO thin films, which were grown on insulating substrates. I-V switching characteristics, electric pulse switching hysteresis, as well as the dynamic resistance during nano second switching pulses of the EPIR devices were measured. Temperature studies showed similar activation energies for both high and low resistance states. Resistance profile microanalysis showed resistance switching both in the interface regions of the oxide film near the electrode, as well as in the bulk of PCMO film with the major resistance change from the interface regions. The resistance switching mechanism is discussed.

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Colossal magnetoresistive thin films have shown a large electric-pulse-induced resistivity change effect in zero magnetic field and at room temperature. The resistance of such films can be both decreased and increased through multiple nonvolatile intermediate levels by short electrical pulses. The effect provides a potential to develop a novel nonvolatile memory with high density, fast speed, and low power-consumption. An example of this effect has been seen for Pr0.7Ca0.3MnO3 films within which the thermal behavior of the film revealed a method for signal enhancement through annealing. An increase of 700% of the resistance ratio has been demonstrated for a film annealed at 170oC for 30 min. The effect is also observed to be active at room temperature but inefficient at low temperatures, which is interestingly contrary to the behavior of the colossal magnetoresistance effect and provides a clue to understanding the effect.

The electric-pulse-induced resistance-change with the number of the pulse until it reaches a saturation value, (EPIR) switching effect in oxides is attractive for its is reversible with pulse polarity, and is non-volatile with time, potential use in non-volatile resistance random access as shown in Fig. 1 for a Ag/Pro.7Cao.31n03(PCMO) memories (RRAM). Such RRAM is highly valued due to its /Pt/TiN/SiO2/Si device. The electrical pulse width can be as fast switching speed, nondestructive readout, and short as Al0 ns and the pulse magnitude can be as low as drastically reduced power consumption. The polarityseveral volts. This bistable resistive memory switching effect dependent, reversible resistance switching at room is promising for emerging resistive random access memory temperature has been observed in the two-terminal metal-(RRAM) devices, in which fast switching speeds, low power oxide-metal thin film devices with transition metal oxide consumption and nano-sized devices with simple device layers including perovskite oxides RE1-xAxMO3 (RE-rare structure can be realized. [3] earth ions, A-alkaline ions, M-transition metal ions), andThe possible underlying mechanisms of EPIR effect, binary oxides MOx (M-transition metal). These strongly however, are surprisingly divergent, although the resistance correlated electron systems have been studied by scanning switching memory behavior in many oxide systems has beenKelvin probe microscopy, current AFM and confocal laser clearly observed.scanning microscopy, which indicate that the resistance In this article, we will present our recent micro-nano switching occurs principally in the extended interface analysis on the EPIR effect, and propose a possible resistance regions of the device (near the two electrical contacts).switching mechanism responsible for the observed EPIRThe basis for the EPIR effect is proposed as principally effect. electric current-enhanced oxygen ion/vacancy migration in these interface regions. 106-3.2V 8ns

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