Multiferroic research promises improved data storage

Berkeley, CA – Berkeley Lab researchers have demonstrated that electric fields can be used as on/off switches in multiferroic materials, a development that they say holds promise for future magnetic data storage and spintronic devices.

Multiferroics are materials in which unique combinations of electric and magnetic properties can coexist. Scientists have been eyeing them for some time as having potential applications in magnetic data storage and spintronic devices once a simple and fast way could be found to turn their electric and magnetic properties on and off.

“Using electric fields, we have been able to create, erase and invert p–n junctions in a calcium-doped bismuth ferrite film,” said Ramamoorthy Ramesh of Berkeley Lab‘s Materials Sciences Division (MSD), who led the research.

“Through the combination of electronic conduction with the electric and magnetic properties already present in the multiferroic bismuth ferrite, our demonstration opens the door to merging magnetoelectrics and magnetoelectronics at room temperature.”

Computer designers have been eagerly awaiting the development of memory chips that store data through electron spin and its associated magnetic moment rather than electron charge. Because multiferroics simultaneously exhibit two or more ferro electric or magnetic properties in response to changes in their environment, they are considered prime candidates for this technology.

Whereas a typical CMOS device features an on/off switching ratio (the difference between resistance and non-resistance to electrical current) of about one million, Ramesh and his group achieved an on/off switching ratio of about a thousand in their calcium-doped bismuth ferrite films. While this ratio is fine for device operation and double the best ratio achieved with magnetic fields, Chan-Ho Yang, lead author on this Nature Materials paper and a post-doc in Ramesh’s group, says it can be improved.

“To make the on state more conductive, we have many ideas to try such as different calcium-doping ratios, different strain states, different growth conditions, and eventually different compounds using the same idea,” Yang said.