Researchers have created a new technology that allows for switching magnetization using voltage control, which could lead to the development of advanced computational memory. This innovative approach facilitates data writing with minimal energy consumption while ensuring the memory remains intact, making it suitable for future technologies that demand dependable and stable memory.
In recent years, various memory types for computing devices have been developed to address the limitations of traditional random access memory (RAM). One notable type is Magnetoresistive RAM (MRAM), which provides multiple benefits over standard RAM, such as being non-volatile, offering high-speed performance, expanding storage capacity, and providing better durability. Despite significant advancements in MRAM technology, lowering energy usage during data writing remains a significant hurdle.
A study recently published in Advanced Science by researchers at Osaka University introduces a new method for MRAM devices that minimizes energy used during data writing. This innovative technology allows for an electric-field-based writing mechanism that consumes less power compared to the current approach, potentially serving as a replacement for traditional RAM.
Standard dynamic RAM (DRAM) devices consist of basic storage units such as transistors and capacitors but are considered volatile, meaning they require a continuous energy supply to maintain data. In contrast, MRAM utilizes magnetic states, like the orientation of magnetization, to write and preserve data, which allows for non-volatile storage.
“Since MRAM devices depend on a non-volatile magnetization state instead of a volatile charge state found in capacitors, they present a promising alternative to DRAM due to their lower power consumption when not in use,” explains Takamasa Usami, the lead author of the study.
Today’s MRAM devices typically need electric currents to change the magnetization direction of magnetic tunnel junctions, similar to how capacitor charge states are switched in DRAM devices. However, substantial electric currents are necessary during the writing phase to alter the magnetization, which leads to energy loss through Joule heating.
To tackle this issue, the researchers have designed a new component that enables electric field control in MRAM devices. This essential technology is a multiferroic heterostructure, featuring magnetization vectors that respond to an electric field. The effectiveness of this heterostructure in relation to an electric field is defined by the converse magnetoelectric (CME) coupling coefficient; higher values signify a stronger magnetic reaction.
The researchers had previously reported a multiferroic heterostructure with a significant CME coupling coefficient exceeding 10-5 s/m. Yet, variations in the structure of the ferromagnetic layer (Co2FeSi) made it difficult to achieve the intended magnetic properties, complicating the reliable function of electric-field operations. To enhance the stability of this system, the researchers engineered a thin vanadium layer to be inserted between the ferromagnetic and piezoelectric layers. This addition established a clear interface, allowing for reliable management of magnetic properties within the Co2FeSi layer. Moreover, the CME effect was improved beyond previous values observed in similar devices lacking a vanadium layer.
The team also showed that it is possible to create two distinct magnetic states at zero electric field by adjusting the electric field’s sweeping operation, meaning that a non-volatile binary state can be consistently achieved without an electric field.
“By accurately controlling the multiferroic heterostructures, we successfully meet two essential criteria for practical magnetoelectric (ME)-MRAM devices: the capacity for a non-volatile binary state at zero electric field and a substantial CME effect,” states Kohei Hamaya, the senior author.
This research in spintronic devices holds the potential for implementation in practical MRAM technology, enabling the creation of ME-MRAM, which represents a low-power writing solution suitable for various applications that require persistent and reliable memory.
