Researchers at the Tokyo Institute of Technology have made significant advancements in memory technology using multiferroic materials, specifically BFCO nanodots. These materials enable more energy-efficient data writing using electric fields and non-destructive reading through magnetic fields. Credit: SciTechDaily.com
Tokyo Institute of Technology researchers have developed BFCO nanodots for efficient and non-destructive memory technology, promising advancements in low-power magnetic memory devices.
Traditional memory devices are volatile and the current non-volatile ones rely on either ferromagnetic or ferroelectric materials for data storage. In ferromagnetic devices, data is written or stored by aligning magnetic moments, while in ferroelectric devices, data storage relies on the alignment of electric dipoles. However, generating and manipulating magnetic fields is energy-intensive, and in ferroelectric memory devices, reading data destroys the polarized state, requiring the memory cell to be re-writing.
Advancements in Multiferroic Materials
Multiferroic materials, which contain both ferroelectric and ferromagnetic orders, offer a promising solution for more efficient and versatile memory technology. Cobalt-substituted BiFeO3 (BiFe0.9Co0.1O3, BFCO) is a multiferroic material that exhibits strong magnetoelectric coupling, meaning changes in electric polarization affect magnetization. As a result, data can be written using electric fields, which is more energy-efficient than generating magnetic fields, and read using magnetic fields, which avoids the destructive read-out process.
In a significant milestone for multiferroic memory devices, a team of researchers led by Professor Masaki Azuma and Assistant Professor Kei Shigematsu from Tokyo Institute of Technology in Japan has successfully developed nanodots with single ferroelectric and ferromagnetic domains.
BFCO 60-nm nanodots, with single domain structures, hold promise for high-density and low-power nonvolatile magnetic memory devices. Credit: Tokyo Tech
Collaborative Research Efforts
“At “Sumitomo Chemical Next-Generation Eco-Friendly Devices Collaborative Research Cluster” within the Institute for Innovative Research at Tokyo Institute of Technology, there is a focus on multiferroic materials that exhibit cross-correlation responses between magnetic and electrical properties based on the principles of strongly correlated electron systems. The center aims to develop materials and processes for next-generation low-power non-volatile magnetic memory devices, as well as to conduct reliability assessments and social implementation,” says Azuma.
Methodology and Findings
In their study published in the journal ACS Applied Materials and Interfaces on April 9, 2024, researchers utilized pulsed laser deposition to deposit multiferroic BFCO onto a conductive Nb:SrTiO3 (001) substrate. They controlled the deposition process by using anodized aluminum oxide (AAO) masks with adjustable pore sizes, resulting in nanodots with diameters of 60 nm and 190 nm.
BFCO is a promising option for low-power, nonvolatile magnetic memory devices as its magnetization direction can be reversed with an electric field. On observing the polarization and magnetization directions using piezoresponse force microscopy and magnetic force microscopy, respectively, the researchers found that the nanodots exhibit correlated ferroelectric and ferromagnetic domain structures.
Observations on Domain Structures
Interestingly, when comparing nanodots of different sizes, they noticed significant differences. The smaller 60-nm nanodot, made using an oxalic SciTechDaily