When researchers irradiate a thin layer of nickel iodide with an ultrafast laser pulse, corkscrew-shaped phenomena called “chiral helical magnetoelectric oscillations” appear. These phenomena could be useful for a range of applications, including fast and compact computer memories. Credit: Ella Maru Studio
The researchers found that nickel iodide exhibits exceptional magnetoelectric coupling, making it particularly suitable for use in high-speed, energy-efficient technologies such as magnetic memories and
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The layered multiferroic material nickel iodide could be the best candidate yet for devices such as computer magnetic memory that are extremely fast and compact.
Multiferroics and nickel iodide
For decades, scientists have been studying a group of unusual materials called multiferroics that could be useful for a range of applications, including computer memories, chemical sensors and quantum computers. In a study published in NatureResearchers from the University of Texas at Austin and the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) have demonstrated that the layered multiferroic material nickel iodide (NiI)2) might be the best candidate yet for extremely fast and compact devices.
Multiferroics have a special property called magnetoelectric coupling, which means you can manipulate the magnetic properties of the material with an electric field and vice versa, the electrical properties with magnetic fields. The researchers discovered NiI2 has a stronger magnetoelectric coupling than any other known material of its type, making it a prime candidate for technological advances.
When researchers irradiate a thin layer of nickel iodide with an ultrafast laser pulse, corkscrew-shaped phenomena called “chiral helical magnetoelectric oscillations” appear. These phenomena could be useful for a range of applications, including fast and compact computer memories. Credit: Ella Maru Studio
Breakthrough in magnetoelectric coupling
“Unveiling these effects at the scale of thin nickel iodide flakes has been a formidable challenge,” said Frank Gao, a UT postdoctoral researcher in physics and co-senior author of the paper, “but our success represents a significant advance in the field of multiferroics.”
“Our discovery paves the way for extremely fast and energy-efficient magnetoelectric devices, including magnetic memories,” added graduate student Xinyue Peng, another co-lead author of the project.
Fundamental properties and research methodologies
Electric and magnetic fields are fundamental to our understanding of the world and to modern technologies. Within a material, electric charges and atomic magnetic moments can be ordered in such a way that their properties add up, forming an electric polarization or magnetization. Such materials are called ferroelectric or ferromagnetic, depending on which of these quantities is in an ordered state.
However, in exotic materials called multiferroics, these electric and magnetic orders coexist. The magnetic and electric orders can be entangled in such a way that a change in one leads to a change in the other. This property, known as magnetoelectric coupling, makes these materials attractive candidates for faster, smaller, and more efficient devices. For these devices to work efficiently, it is important to find materials with particularly strong magnetoelectric coupling, as the research team describes the case with NiI2 in their study.
The researchers achieved this by exciting the material with ultrashort laser pulses on the order of femtoseconds (one millionth of a billionth of a second) and then tracking the resulting changes in the material’s electrical and magnetic ordering and magnetoelectric coupling through their impact on specific optical properties.
Potential applications and future research
To understand why the magnetoelectric coupling is so much stronger in NiI2 than in similar materials, the team carried out extensive calculations.
“Two factors play an important role here,” said Emil Viñas Boström, co-author of the study at MPSD. “One is the strong coupling between the electron spin and the orbital motion of the iodine atoms – this is a relativistic effect known as spin-orbit coupling. The second factor is the special form of magnetic ordering in nickel iodide, known as a spin spiral or spin helix. This ordering is crucial both for initiating the ferroelectric order and for the strength of the magnetoelectric coupling.”
Materials like NiI2 Highly magnetoelectrically coupled devices have a wide range of potential applications, the researchers say. These include compact, energy-efficient magnetic computer memories that can be stored and retrieved much faster than existing memories; interconnects in quantum computing platforms; and chemical sensors that can ensure quality control and drug safety in the chemical and pharmaceutical industries.
The researchers hope that these breakthrough findings can be used to identify other materials with similar magnetoelectric properties and that other materials engineering techniques could eventually lead to further improvement of the magnetoelectric coupling in NiI.2.
Reference: “Giant Chiral Magnetoelectric Oscillations in a Van der Waals Multiferroic” July 17, 2024, Nature.
DOI: 10.1038/s41586-024-07678-5
This work was designed and supervised by Edoardo Baldini, assistant professor of physics at UT, and Angel Rubio, director of the MPSD.
Other authors of the paper are Dong Seob Kim and Xiaoqin Li. Other authors of MPSD are Xinle Cheng and Peizhe Tang. Other authors are Ravish K. Jain, Deepak Vishnu, Kalaivanan Raju, Raman Sankar, and Shang-Fan Lee of Academia Sinica; Michael A. Sentef of the University of Bremen; and Takashi Kurumaji of the California Institute of Technology.
Funding for this research was provided by the Robert A. Welch Foundation, the U.S. National Science Foundation, the U.S. Air Force Office of Scientific Research, the European Union’s Horizon Europe research and innovation program, the Cluster of Excellence “CUI: Advanced Imaging of Matter”, Grupos Consolidados, the Max Planck-New York City Center for Quantum Out-of-Equilibrium Phenomena, the Simons Foundation, and the Ministry of Science and Technology of Taiwan.