#multiferroics

Room-temperature multiferroic could pave way to low-energy computing

A team of researchers at Rice University has engineered a new version of a well-known multiferroic that exhibits orders of magnitude higher performance at room temperature than its parent material. The study, published in the Proceedings of the National Academy of Sciences, describes a modified version of bismuth ferrite that shows a 10-fold increase in magnetization and 100-fold increase in magnetoelectric coupling compared to standard varieties. The synthesis process entailed mixing bismuth ferrite with barium titanate while simultaneously growing the material as a thin film on a substrate that distorts its crystal structure.

Nanoengineered spintronic device can store data in four different ways

Over the past decades, electronics engineers have been trying to develop increasingly smaller devices that can store information reliably, even when they are not powered on. A promising type of non-volatile memory device is spintronics, solid-state systems that store and process information leveraging the spin (i.e., an intrinsic form of angular momentum) of electrons. Researchers at University of Maryland and other institutes recently introduced a new spintronic device based on nanoscale structures based on materials that exhibit ferromagnetism (i.e., a permanent yet switchable magnetic order) and ferroelectricity (i.e., a permanent yet switchable electric polarization). This device, presented in a paper published in Nature Nanotechnology, can switch between four stable resistance states and could thus serve as a multistate memory.

Electrical control of magnetism in 2D materials promises to advance spintronics

Conventional electronics process information leveraging the electrical charge of electrons. Over the past few decades, some electronics engineers have been exploring the potential of a different type of device that instead processes and stores data exploiting the intrinsic magnetic moment (i.e., spin) of electrons. These devices, known as spintronics, could consume less energy, process data faster and be easier to reduce in size than current electronics. A central objective for engineers who are developing spintronics is to identify promising strategies to control magnetism in devices without wasting power. One promising approach to control magnetism entails the use of multiferroics, materials that exhibit both ferroelectricity, meaning that positive and negative charges in them are permanently separated, and ferromagnetism, which means that magnetic moments in them are aligned. When one of these properties can be used to control the other, this is known as magnetoelectric coupling.

Researchers realize room-temperature two-dimensional multiferroic metal

Multiferroic metals are materials that exhibit both electric polarization and magnetic order in the same crystal—a state known as multiferroicity. Because these properties coexist, they can interact through magnetoelectric (ME) coupling, allowing electric fields to influence magnetism. Unfortunately, bulk multiferroic materials face limitations, including relatively small spontaneous polarization, weak ME coupling coefficients, and limited operational stability under ambient conditions due to oxygen-vacancy-induced leakage currents, which restrict their practical applications. Now, however, researchers from the Institute of Physics of the Chinese Academy of Sciences, along with their collaborators from Zhejiang University, have realized electric-field control of magnetic states using a two-dimensional (2D) van der Waals material, while demonstrating intrinsic room-temperature (RT) multiferroicity with strong ME coupling.

Smarter memory: Researchers introduce next-generation RAM with reduced energy consumption

Numerous memory types for computing devices have emerged in recent years, aiming to overcome the limitations imposed by traditional random access memory (RAM). Magnetoresistive RAM (MRAM) is one such memory type which offers several advantages over conventional RAM, including its non-volatility, high speed, increased storage capacity and enhanced endurance. Although remarkable improvements have been made to MRAM devices, reducing energy consumption during data writing remains a critical challenge. A study published in Advanced Science by researchers from Osaka University proposes a new technology for MRAM devices with lower-energy data writing. The proposed technology enables an electric-field-based writing scheme with reduced energy consumption compared to the present current-based approach, potentially providing an alternative to traditional RAM.

Paving the way to extremely fast, compact computer memory

For decades, scientists have been studying a group of unusual materials called multiferroics that could be useful for a range of applications including computer memory, chemical sensors and quantum computers. In a study published in Nature, researchers from The University of Texas at Austin and the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) demonstrated that the layered multiferroic material nickel iodide (NiI2) may be the best candidate yet for devices that are extremely fast and compact. Multiferroics have a special property called magnetoelectric coupling, which means that you can manipulate magnetic properties of the material with an electric field and vice versa, electric properties with magnetic fields. The researchers found NiI2 has greater magnetoelectric coupling than any known material of its kind, making it a prime candidate for technology advances.

How magnetization direction can be controlled using strain in an interfacial multiferroic material

Controlling the direction of magnetization using low electric field is necessary for developing efficient spintronic devices. In spintronics, properties of an electron's spin or magnetic moment are used to store information. The electron spins can be manipulated by straining orbital magnetic moments to create a high-performance magnetoelectric effect. A Japanese research team, led by Jun Okabayashi from the University of Tokyo, including Associate Professor Yoshihiro Gohda from Tokyo Tech and Osaka University researchers have revealed a strain-induced orbital control mechanism in interfacial multiferroics. The study is published in the journal NPG Asia Materials. In multiferroic material, the magnetic field can be controlled using an electric field—potentially leading to efficient spintronic devices. The interfacial multiferroics that Okabayashi and his colleagues studied consist of a junction between a ferromagnetic material and a piezoelectric material. The direction of magnetization in the material could be controlled by applying voltage.

Novel single crystals show promising electric field control of magnetism

A research team led by associate Prof. Yin Lihua from the Hefei Institutes of Physical Science of the Chinese Academy of Sciences has demonstrated a clear control of magnetism at low electric fields (E) at room temperature. The E-induced phase transformation and lattice distortion were found to lead to the E control of magnetism in multiferroic BiFeO3-based solid solutions near the morphotropic phase boundary (MPB). The study was published in Acta Materialia.

Multiferroic materials, with magnetic and ferroelectric properties, are promising for multifunctional memory devices. Magnetoelectric-based control methods in insulating multiferroic materials require less energy and have potential for high-speed, low-power information storage applications. BiFeO3 is a room-temperature multiferroic material with potential for use in spintronics devices, but its weak ferromagnetic and magnetoelectric effects and high voltage required for manipulation are weaknesses.

In this study, the researchers grew single crystals of the multiferroic 0.58BiFeO3-0.42Bi0.5K0.5TiO3 (BF-BKT), which lies in the tetragonal region adjacent to the MPB.

"Below the Néel temperature, TN~257.5 K, the BF-BKT crystals showed antiferromagnetic behavior," said Yin, "and at room temperature, we found that the BF-BKT crystals exhibited both short-range magnetic order and long-range ferroelectric order."