Magnetic switch holds promise for double capacity solid state storage
Japanese scientists have developed a device that can switch safely and quickly between magnetic and electronic signals. In so doing they've opened the door to a doubling of the storage capacity of conventional memory devices such as solid-state drives and USB flash drives.
Data in magnetic storage is represented in the direction of magnetization at various regions in a magnetic film, while conventional electronic storage devices store information in binary form within millions of tiny logic gates. The Hokkaido University researchers theorized that it would be possible to add an A/B magnetic store for data to the existing 0/1 (electronic) binary store if a storage material could switch back and forth rapidly between magnetic and non-magnetic states. In essence, this could double storage capacity.
Compounds known as transition metal oxides have the appropriate functional properties – they switch between an insulating, non-magnet state to a high-conductivity metallic magnet state as they gain or lose oxide ions.
Unfortunately neither of the two standard methods for controlling oxygen off-stoichiometry (meaning without exact quantities in a lab) for their chosen compound strontium cobalt oxide are viable. One requires high-temperature heating, which is ill-suited to devices meant for room-temperature operation. The other uses a liquid alkaline electrolyte that triggers an electrochemical reaction at room temperature, but which leaks, so a device using this method couldn't be sealed and miniaturized.
The researchers developed their own method instead. They swapped the liquid alkaline for a sodium tantalate thin film, which they laid over strontium cobalt oxide. Applying a three-volt current switched the device from its insulating form to its metal magnet form in around two to three seconds. Reversing the current direction returned it to the insulating form.
This switching time is slow, but it could be significantly hastened by making the device smaller, which they'd need to do for commercial application anyway.
The researchers believe that their approach could enable development of new electromagnetic switching devices such as higher-capacity flash storage (for your mobile phone or USB flash drive or even SSD) as well as new electro-optical and electrothermal devices.
A paper describing the research was published in the journal Advanced Electronic Materials.
Source: Hokkaido University