Neutron scattering reveals the helical magnetic structure of layered perovskites

Combining electrical and magnetic properties in a promising way, multi-ferlock materials are at the heart of new solutions for data storage, data transmission, and quantum computers. On the other hand, understanding the origin of such properties at the fundamental level is key to developing applications, with neutrons being the ideal probe.

Neutrons have magnetic dipole moments that make them sensitive to the magnetic fields produced by unpaired electrons in a material. This makes neutron scattering technology a powerful tool for examining the magnetic behavior of materials at the atomic level.

The so-called layered perovskite story and the groundbreaking results currently published are paradigmatic examples that highlight the role of both basic research and neutron power in application development. As a promising class of materials exhibiting magnetic and electrical order properties coupled at ambient temperature, the magnetic structure of the layered perovskite Ybacufeo5, and therefore the origin of their interesting magnetoelectric behavior, has yet to be vaguely determined.

The results currently published in communications materials identify the helical magnetic structures of these materials and ultimately establish a common origin of promising magnetic and electrical properties up to room temperature. The experiments were carried out fully in the disease using five instruments from over 40 state-of-the-art suites, utilizing advanced sample environmental technology.

“This study removed the essential ambiguity covering the gaps created by the lack of single crystal investigations,” said J. Alberto Rodríguez-Velamazán, Ill Researcher, Head of D3 Instrument. “All studies are done on neutrons alone and rely on the combination of various diffraction techniques and capabilities available in ILL.”

Small spiral magnet

Magnetre Electric Multiferlock is a material that coexists with electrical and magnetic orders. The combination of ferroelectricity (characterized by net electrode polarization) and long-range magnetic order (by alignment of magnetic moments resulting from unbound electron spins) is highly sought from a technical standpoint.

Some multi-ferlocks have strong electrical and magnetic properties combined. Alignment of magnetic moments induces charge separation. An established case of a strongly coupled electrical and magnetic order is the spiral magnetic order. You can create electric dipole by arranging it into a spiral pattern that enhances spin.

The combined magnetic and electrical order allows the use of electric fields to act on magnetic properties, and magnetic fields to act on electrical properties. Therefore, combined multiferlocks are a promising material for designing new devices.

In particular, using fields (rather than magnetism) to act based on magnetic order, for example, will consume much less energy if you change the state of a storage device or manipulate the spin state. . Furthermore, such materials are usually less volatile (less perturbed by external magnetic fields), which increases the stability of the device and allows for even smaller size.

Spiral Multi-Fellock is rare. In fact, rather serious constraints on the symmetry and geometry of the microscopic structure of the material are imposed in such a way that such singular properties arise. In most multiferrock materials, the distinctive order is only present at very low temperatures. In practice, this strongly limits the possibilities for implementation on devices.

Maintain “cool” at high temperatures: Remove perovskite mystery with neutrons

Layered perovskites (RBACUFEO5) are rare cases of magnetic and electrical order properties coupled at ambient temperatures, and therefore are a promising class of materials for applications. The behavior of multiferros at high temperatures has been well established, but the underlying magnetic structures, and therefore the origin of their interesting magnetoelectric behavior, has not yet been clearly determined.

In fact, a non-traditional mechanism (named the “spiral order by obstacle”) was devised to explain the extraordinary thermal stability of the estimated spiral magnetic order. Nevertheless, there was no conclusive data supporting the existence of a spiral order in these materials.

In fact, the available results obtained on polycrystalline samples using powder neutron diffraction measurements were compatible with spiral order and with spin modulation of the sinus. This is a configuration that does not produce ferroelectric properties. There was still a lack of research that could solve two possibilities.

The interesting observed macroscopic properties of the materials will still be there, but the lack of spiral order does not retain existing explanations of what actually happened in the materials, so we are not able to assure them of their microscopic origins. It means you didn’t really understand. A good starting point for developing applications based on this document.

This study is published in correspondence material filled with this gap by taking two very important steps essentially.

The first important step was to move from polycrystalline powder samples to high quality single crystals. The crystals were grown and characterized in Barcelona materials (ICMAB-CSIC, Spain). Their magnetic structures were then extensively analyzed in diseased neutrons.

Instrument Orient Express was used to take snapshots of crystals and was able to assess its quality and orientation. Laue’s diffractometer cyclops expanded these measurements to cryogenic temperatures and quickly investigated the complete mutual space. This allowed researchers to select the most promising samples for further monochromatic experiments. A wide range of measurements were then performed on monochromatic single crystal diffraction meters D10 and D9.

The second decisive step was the use of polarized neutrons. Indeed, the possibility of generating a beam of polarized neutrons (all spins are parallel) is permitted, and magnetic information is identified much more accurately, facilitating decoding of complex magnetic structures. Spherical neutron polarization measurement (SNP) experiments were performed on a high-temperature neutron diffractometer D3. The magnetoelectric response was investigated by an electric field.

“Our findings not only confirm that the magnetic order of our crystals is helical, but also show that cationic disorders are responsible for stabilizing this spiral structure. This insight is , similar orders range from the perovskite family of samples that are well above room temperature. In powdered samples, Rodriguez Beramazan concludes.