June 16, 2024

Novel Magnetic Semiconductor Gives New Perspective on Anomalous Hall Effect

Credit: Masaki Uchida of Tokyo Institute of Technology
A big, unconventional anomalous Hall resistance in a brand-new magnetic semiconductor in the absence of massive magnetic ordering has been shown by Tokyo Tech products scientists, verifying a recent theoretical forecast. Their findings provide brand-new insights into the anomalous Hall effect, a quantum phenomenon that has actually formerly been associated with long-range magnetic order.
When moving under the impact of electrical and magnetic fields, charged particles such as electrons can behave in communicating methods. For instance, when a magnetic field is applied perpendicular to the plane of a current-carrying conductor, the electrons streaming within start to deviate sideways due to magnetic force and quickly enough, a voltage difference appears throughout the conductor. This phenomenon is famously called the “Hall effect.” The Hall effect does not necessarily need messing with magnets. It can be observed in magnetic products with long-range magnetic order, such as ferromagnets, for complimentary!
Called “anomalous Hall result” (AHE), this phenomenon seems a close cousin of the Hall impact. Its mechanism is way more included. Presently, the most accepted one is that the AHE is produced by a home of the electronic energy bands called “Berry curvature,” which arises from an interaction in between the electrons spin and its movement inside the product, more commonly understood as “spin-orbit interaction.”

Is magnetic ordering essential for AHE? A current theory recommends otherwise. “It has been in theory proposed that a large AHE is possible even above the temperature level at which the magnetic order disappears, particularly in magnetic semiconductors with low charge carrier density, strong exchange interaction between electrons, and limited spin chirality, which connects to the spin direction with respect to the instructions of movement,” explains Associate Professor Masaki Uchida from Tokyo Institute of Technology (Tokyo Tech), whose research focus lies in condensed matter physics.
Curious, Dr. Uchida and his collaborators from Japan chose to put this theory to the test. In a new research study released in Science Advances, they investigated the magnetic homes of a brand-new magnetic semiconductor EuAs that is just understood to have a strange distorted triangular lattice structure and observed an antiferromagnetic (AFM) habits (surrounding electron spins aligned in opposite instructions) listed below 23 K. Furthermore, they observed that the materials electrical resistance dropped considerably with temperature in the presence of an external magnetic field, a habits called “gigantic magnetoresistance” (CMR). However, more surprisingly, the CMR was observed even above 23 K, where the AFM order disappeared.
” It is naturally understood that the CMR observed in EuAs is brought on by a coupling between the diluted providers and localized Eu2+ spins that persist over a wide variety of temperatures,” remarks Dr. Uchida.
What truly took the program, nevertheless, was the rise in Hall resistivity with temperature level, which peaked at a temperature of 70 K, far above the AFM purchasing temperature level, demonstrating that big AHE was indeed possible without magnetic order. To understand what caused this unconventionally big AHE, the group performed design calculations, which revealed that the result could be credited to a skew scattering of electrons by a spin cluster on the triangular lattice in a “hopping program” where the electrons did not circulation but rather “hopped” from atom to atom.
These results bring us one step more detailed to understanding the unusual behavior of electrons inside magnetic solids. “Our findings have helped shed light on triangular-lattice magnetic semiconductors and could potentially lead to a new field of research targeting watered down providers paired to non-traditional spin buyings and variations,” comments a positive Dr. Uchida.
Undoubtedly, new discoveries in the endlessly remarkable quantum world of electrons may be on the horizon!
Recommendation: “Above-ordering-temperature large anomalous Hall impact in a triangular-lattice magnetic semiconductor” by Masaki Uchida, Shin Sato, Hiroaki Ishizuka, Ryosuke Kurihara, Taro Nakajima, Yusuke Nakazawa, Mizuki Ohno, Markus Kriener, Atsushi Miyake, Kazuki Ohishi, Toshiaki Morikawa, Mohammad Saeed Bahramy, Taka-hisa Arima, Masashi Tokunaga, Naoto Nagaosa and Masashi Kawasaki, 22 December 2021, Science Advances.DOI: 10.1126/ sciadv.abl5381.

When a magnetic field is applied perpendicular to the plane of a current-carrying conductor, the electrons streaming within start to deviate sideways due to magnetic force and soon enough, a voltage difference appears throughout the conductor. It can be observed in magnetic products with long-range magnetic order, such as ferromagnets, for totally free!
“It has actually been in theory proposed that a big AHE is possible even above the temperature at which the magnetic order vanishes, particularly in magnetic semiconductors with low charge carrier density, strong exchange interaction in between electrons, and limited spin chirality, which relates to the spin instructions with regard to the instructions of motion,” discusses Associate Professor Masaki Uchida from Tokyo Institute of Technology (Tokyo Tech), whose research study focus lies in condensed matter physics.
In a new research study released in Science Advances, they investigated the magnetic properties of a brand-new magnetic semiconductor EuAs that is just understood to have a peculiar distorted triangular lattice structure and observed an antiferromagnetic (AFM) behavior (neighboring electron spins lined up in opposite instructions) below 23 K. Furthermore, they observed that the products electrical resistance dropped drastically with temperature level in the presence of an external magnetic field, a habits understood as “gigantic magnetoresistance” (CMR).