New type of memory effect found in transition metal oxides

1 min read

A new kind of memory effect, unrelated to memory effects previously reported, is said to have been discovered in transition metal oxides (TMOs) by Bar-Ilan University in Israel.

According to the research team, TMOs are subject to complex electronic interactions, resulting in a variety of phenomena, such as interesting memory effects.

The researchers claim to have used a simple experimental design to study changes in the properties of VO2 and NdNiO3, which undergo a metal-insulator phase-transition.

When heated, the studied TMOs transit from one state to another, beginning in a small area where ‘islands’ develop and then grow, and vice-versa during cooling.

The team cooled the samples while transition was in process, and then examined what happened when they were reheated. They found that when the reheated metal-oxide reached the phase coexistence state, an increase in resistance was measured.

This increase in resistance was observed at each different point at which cooling was initiated. This previously unknown phenomenon is said to demonstrate the creation of a ‘memory’.

"When the temperature ramp is reversed, and the sample is cooled rather than heated, the direction change creates a ‘scar’ wherever there is a phase-boundary between the conducting and insulating islands,” explained Dr. Amos Sharoni.

“The ramp reversal sequence encrypts a ‘memory’ of the reversal temperature, which is manifested as increased resistance. Moreover, it is possible to create and store more than one ‘memory’ in the same physical space.”

The researchers found that further heating the TMO enables it to complete transition and to cross the scarred boundaries, ‘healing’ the scars and erasing the memory. In contrast, cooling does not erase them.

According to the team, the erase-upon-reading property of this system could make be used in security technologies.