Spintronics advances -- Controlling magnetization direction of magnetite at room temperature

November 17, 2020

Over the last few decades, conventional electronics has been rapidly reaching its technical limits in computing and information technology, calling for innovative devices that go beyond the mere manipulation of electron current. In this regard, spintronics, the study of devices that exploit the "spin" of electrons to perform functions, is one of the hottest areas in applied physics. But, measuring, altering, and, in general, working with this fundamental quantum property is no mean feat.

Current spintronic devices--for example, magnetic tunnel junctions--suffer from limitations such as high-power consumption, low operating temperatures, and severe constraints in material selection. To this end, a team of scientists at Tokyo University of Science and the National Institute for Materials Science (NIMS), Japan, has recently published a study in ACS Nano, in which they present a surprisingly simple yet efficient strategy to manipulate the magnetization angle in magnetite (Fe3O4), a typical ferromagnetic material. The team fabricated an all-solid reduction-oxidation ("redox") transistor containing a thin film of Fe3O4 on magnesium oxide and a lithium silicate electrolyte doped with zirconium (Fig. 1). The insertion of lithium ions in the solid electrolyte made it possible to achieve rotation of the magnetization angle at room temperature and significantly change the electron carrier density. Associate Professor Tohru Higuchi from Tokyo University of Science, one of the authors of this published paper, says "By applying a voltage to insert lithium ions in a solid electrolyte into a ferromagnet, we have developed a spintronic device that can rotate the magnetization with lower power consumption than that in magnetization rotation by spin current injection. This magnetization rotation is caused by the change of spin-orbit coupling due to electron injection into a ferromagnet."

Unlike previous attempts that relied on using strong external magnetic fields or injecting spin-tailored currents, the new approach leverages a reversible electrochemical reaction. After applying an external voltage, lithium ions migrate from the top lithium cobalt oxide electrode and through the electrolyte before reaching the magnetic Fe3O4 layer. These ions then insert themselves into the magnetite structure, forming LixFe3O4 and causing a measurable rotation in its magnetization angle owing to an alteration in charge carriers.

This effect allowed the scientists to reversibly change the magnetization angle by approximately 10°. Although a much greater rotation of 56° was achieved by upping the external voltage further, they found that the magnetization angle could not be switched back entirely (Fig. 2). "We determined that this irreversible magnetization angle rotation was caused by a change in the crystalline structure of magnetite due to an excess of lithium ions," explains Higuchi, "If we could suppress such irreversible structural changes, we could achieve a considerably larger magnetization rotation."

The novel device developed by the scientists represents a big step in the control of magnetization for the development of spintronic devices. Moreover, the structure of the device is relatively simple and easy to fabricate. Dr Takashi Tsuchiya, Principal Researcher at NIMS, the corresponding author of the study says, "By controlling the magnetization direction at room temperature due to the insertion of lithium ions into Fe3O4, we have made it possible to operate with much lower power consumption than the magnetization rotation by spin current injection. The developed element operates with a simple structure."

Although more work remains to be done to take full advantage of this new device, the imminent rise of spintronics will certainly unlock many novel and powerful applications. "In the future, we will try to achieve a rotation of 180° in the magnetization angle," says Dr Kazuya Terabe, Principal Investigator at the International Center for Materials Nanoarchitectonics at NIMS and a co-author of the study, "This would let us create high-density spintronic memory devices with large capacity and even neuromorphic devices that mimic biological neural systems." Some other applications of spintronics are in the highly coveted field of quantum computing.

Only time will tell what this frontier technology has in line for us!
About The Tokyo University of Science

Tokyo University of Science (TUS) is a well-known and respected university, and the largest science-specialized private research university in Japan, with four campuses in central Tokyo and its suburbs and in Hokkaido. Established in 1881, the university has continually contributed to Japan's development in science through inculcating the love for science in researchers, technicians, and educators.

With a mission of "Creating science and technology for the harmonious development of nature, human beings, and society", TUS has undertaken a wide range of research from basic to applied science. TUS has embraced a multidisciplinary approach to research and undertaken intensive study in some of today's most vital fields. TUS is a meritocracy where the best in science is recognized and nurtured. It is the only private university in Japan that has produced a Nobel Prize winner and the only private university in Asia to produce Nobel Prize winners within the natural sciences field.

Website: https://www.tus.ac.jp/en/mediarelations/

About Associate Professor Tohru Higuchi from Tokyo University of Science

Tohru Higuchi, one of the co-authors of this study, is a member of the Department of Applied Physics in the Tokyo University of Science. He graduated in Applied Physics from the Tokyo University of Science in 1995, where he then proceeded to obtain Master's and PhD degrees. His research mainly focuses on functional material science specializing in thin film/surface and interfacial physical properties and inorganic industrial materials. He has authored over 200 papers and received several awards, such as those for his contributions in the GREEN-2019 conference and the 2019 International Symposium on Advanced Material Research.

Funding information

This study was in part supported by Japan Society for the Promotion of Science (JSPS) KAKENHI grant number JP20H05301 (Grant-in-Aid for Scientific Research on Innovative Areas "Interface Ionics") and grant number JP19J13859 (Grant-in-Aid for JSPS Fellows). A part of this work was supported by NIMS TEM Station.

Tokyo University of Science

Related Spintronics Articles from Brightsurf:

A four-state magnetic tunnel junction for novel spintronics applications
Researchers have introduced a new type of MTJ with four resistance states, and successfully demonstrated switching between the states with spin currents.

Ultrafast electrons in magnetic oxides: A new direction for spintronics?
Special metal oxides could one day replace semiconductor materials that are commonly used today in processors.

Efficient valves for electron spins
Researchers at the University of Basel in collaboration with colleagues from Pisa have developed a new concept that uses the electron spin to switch an electrical current.

Magnetic memory states go exponential
Researchers showed that relatively simple structures can support exponential number of magnetic states - much greater than previously thought - and demonstrated switching between the states by generating spin currents.

New breakthrough in 'spintronics' could boost high speed data technology
Scientists have made a pivotal breakthrough in the important, emerging field of spintronics -- which could lead to a new high speed energy efficient data technology.

A path to new nanofluidic devices applying spintronics technology
Japanese scientists have elucidated the mechanism of the hydrodynamic power generation using spin currents in micrometer-scale channels, finding that power generation efficiency improves drastically as the size of the flow is made smaller.

Extensive review of spin-gapless semiconductors: Next-generation spintronics candidates
An Australian has published an extensive review of spin-gapless semiconductors (SGSs), a new class of 'zero bandgap' materials which have fully spin polarised electrons and holes, and first proposed in 2008 by the review team's lead, Professor Xiaolin Wang (University of Wollongong).

Graphene and 2D materials could move electronics beyond 'Moore's Law'
A team of researchers based in Manchester, the Netherlands, Singapore, Spain, Switzerland and the USA has published a new review on a field of computer device development known as spintronics, which could see graphene used as building block for next-generation electronics.

Toward a more energy-efficient spintronics
In order to generate and detect spin currents, spintronics traditionally uses ferromagnetic materials whose magnetization switching consume high amounts of energy.

Computing with molecules: A big step in molecular spintronics
Chemists and physicists at Kiel University joined forces with colleagues from France, and Switzerland to design, deposit and operate single molecular spin switches on surfaces.

Read More: Spintronics News and Spintronics Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.