scholarly journals Anomalous Hall Effect in Geometrically Frustrated Magnets

2012 ◽  
Vol 2012 ◽  
pp. 1-12 ◽  
Author(s):  
D. Boldrin ◽  
A. S. Wills
Keyword(s):  
Berry Phase ◽  
Anomalous Hall Effect ◽  
Frustrated Magnets ◽  
3 Dimensional ◽  
Geometrically Frustrated ◽  
Hall Effects ◽  
Experimental Findings ◽  
Spin Orbit Interactions ◽  
Different Origins ◽  
Aharonov Bohm

Geometrically frustrated conducting magnets display extraordinarily large anomalous Hall effects (AHEs) that could be used to realise materials required for the emerging field of spintronics. While the intrinsic Berry phase developed in collinear ferromagnets is well explained through the effects of spin-orbit interactions within the Karplus and Luttinger model, its origins in frustrated magnets are not. The direct space mechanism based on spin chirality that was originally applied to the pyrochlore Nd2Mo2O7appears unsatisfactory. Recently, an orbital description based on the Aharonov-Bohm effect has been proposed and applied to both the ferromagnetic pyrochlores Nd2Mo2O7and Pr2Ir2O7; the first of which features long-ranged magnetic order while the latter is a chiral spin liquid. Two further examples of geometrically frustrated conducting magnets are presented in this paper—the kagome-like Fe3Sn2and the triangular PdCrO2. These possess very different electronic structures to the 3-dimensional heavy-metal pyrochlores and provide new opportunities to explore the different origins of the AHE. This paper summarises the experimental findings in these materials in an attempt to unite the conflicting theoretical arguments.

scholarly journals The flow of the Berry curvature vector field

2022 ◽  
Vol 12 (1) ◽  
Author(s):  
Ondřej Stejskal ◽  
Martin Veis ◽  
Jaroslav Hamrle
Keyword(s):  
Vector Field ◽  
Berry Phase ◽  
Curvature Vector ◽  
Anomalous Hall Effect ◽  
Analytical Form ◽  
Three Dimensions ◽  
Solid State Physics ◽  
Berry Curvature ◽  
Topological Features ◽  
Hall Effects

AbstractThe concept of Berry phase and Berry curvature has become ubiquitous in solid state physics as it relates to variety of phenomena, such as topological insulators, polarization, and various Hall effects. It is well known that large Berry curvatures arise from close proximity of hybridizing bands, however, the vectorial nature of the Berry curvature is not utilized in current research. On bulk bcc Fe, we demonstrate the flow of the Berry curvature vector field which features not only monopoles but also higher dimensional structures with its own topological features. They can provide a novel unique view on the electronic structure in all three dimensions. This knowledge is also used to quantify particular contributions to the intrinsic anomalous Hall effect in a simple analytical form.

scholarly journals The Flow of the Berry Curvature Vector Field

2021 ◽  
Author(s):  
Ondřej Stejskal ◽  
Martin Veis ◽  
Jaroslav Hamrle
Keyword(s):  
Vector Field ◽  
Berry Phase ◽  
Curvature Vector ◽  
Anomalous Hall Effect ◽  
Analytical Form ◽  
Three Dimensions ◽  
Solid State Physics ◽  
Berry Curvature ◽  
Topological Features ◽  
Hall Effects

Abstract The concept of Berry phase and Berry curvature has become ubiquitous in solid state physics as it relates to variety of phenomena, such as topological insulators, polarization, and various Hall effects. It is well known that large Berry curvatures arise from close proximity of hybridiz-ing bands, however, the vectorial nature of the Berry curvature is not utilized in current research. On bulk bcc Fe, we demonstrate the flow of the Berry curvature vector field which features not only monopoles but also higher dimensional structures with its own topological features. They can provide a novel unique view on the electronic structure in all three dimensions. This knowledge is also used to quantify particular contributions to the intrinsic anomalous Hall effect in a simple analytical form.

scholarly journals Interface-induced sign reversal of the anomalous Hall effect in magnetic topological insulator heterostructures

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Fei Wang ◽  
Xuepeng Wang ◽  
Yi-Fan Zhao ◽  
Di Xiao ◽  
Ling-Jie Zhou ◽  
...  
Keyword(s):  
Hall Effect ◽  
Electric Fields ◽  
First Principles ◽  
Berry Phase ◽  
Condensed Matter ◽  
Anomalous Hall Effect ◽  
First Principles Calculations ◽  
Sign Reversal ◽  
Berry Curvature ◽  
Topological Materials

AbstractThe Berry phase picture provides important insights into the electronic properties of condensed matter systems. The intrinsic anomalous Hall (AH) effect can be understood as the consequence of non-zero Berry curvature in momentum space. Here, we fabricate TI/magnetic TI heterostructures and find that the sign of the AH effect in the magnetic TI layer can be changed from being positive to negative with increasing the thickness of the top TI layer. Our first-principles calculations show that the built-in electric fields at the TI/magnetic TI interface influence the band structure of the magnetic TI layer, and thus lead to a reconstruction of the Berry curvature in the heterostructure samples. Based on the interface-induced AH effect with a negative sign in TI/V-doped TI bilayer structures, we create an artificial “topological Hall effect”-like feature in the Hall trace of the V-doped TI/TI/Cr-doped TI sandwich heterostructures. Our study provides a new route to create the Berry curvature change in magnetic topological materials that may lead to potential technological applications.

Sign reversal of anomalous Hall effect derived from the transformation of scattering effect in cluster-assembled Ni0.8Fe0.2 nanostructural films

Nanoscale ◽  
2021 ◽  
Author(s):  
Ning Jiang ◽  
Bo Yang ◽  
Yulong Bai ◽  
Yaoxiang Jiang ◽  
Shifeng Zhao
Keyword(s):  
Hall Effect ◽  
Anomalous Hall Effect ◽  
Sign Reversal ◽  
Surface And Interface ◽  
Scattering Effect ◽  
Single Substance ◽  
Interface Scattering ◽  
Hall Effects

Both surface and interface scattering induced a sign reversal of anomalous Hall effects (AHE) in a few heterostructures. The sign reversal exiting in a single-substance can clarify the role of...

scholarly journals Giant magnetic field from moiré induced Berry phase in homobilayer semiconductors

2019 ◽  
Vol 7 (1) ◽  
pp. 12-20 ◽  
Author(s):  
Hongyi Yu ◽  
Mingxing Chen ◽  
Wang Yao
Keyword(s):  
Magnetic Field ◽  
Berry Phase ◽  
Transition Metal Dichalcogenides ◽  
Real Space ◽  
Quantum Spin ◽  
Moire Patterns ◽  
Metal Dichalcogenides ◽  
Berry Phases ◽  
Different Origins ◽  
Moiré Patterns

Abstract When quasiparticles move in condensed matters, the texture of their internal quantum structure as a function of position and momentum can give rise to Berry phases that have profound effects on the material’s properties. Seminal examples include the anomalous Hall and spin Hall effects from the momentum-space Berry phases in homogeneous crystals. Here, we explore a conjugate form of the electron Berry phase arising from the moiré pattern: the texture of atomic configurations in real space. In homobilayer transition metal dichalcogenides, we show that the real-space Berry phase from moiré patterns manifests as a periodic magnetic field with magnitudes of up to hundreds of Tesla. This quantity distinguishes moiré patterns from different origins, which can have an identical potential landscape, but opposite quantized magnetic flux per supercell. For low-energy carriers, the homobilayer moirés realize topological flux lattices for the quantum-spin Hall effect. An interlayer bias can continuously tune the spatial profile of the moiré magnetic field, whereas the flux per supercell is a topological quantity that can only have a quantized jump observable at a moderate bias. We also reveal the important role of the non-Abelian Berry phase in shaping the energy landscape in small moiré patterns. Our work points to new possibilities to access ultra-high magnetic fields that can be tailored to the nanoscale by electrical and mechanical controls.

Muon-spin relaxation measurements of geometrically frustrated magnets

2001 ◽  
Vol 79 (11-12) ◽  
pp. 1295-1305 ◽  
Author(s):  
K M Kojima
Keyword(s):  
Spin Relaxation ◽  
Muon Spin ◽  
Muon Spin Relaxation ◽  
Spin Systems ◽  
Frustrated Magnets ◽  
Slow Dynamics ◽  
Kagomé Lattice ◽  
Geometrically Frustrated ◽  
Relaxation Measurements ◽  
Frustrated Spin

Muon-spin relaxation (µSR) has been applied to investigations of slow dynamics and quasi-static features of geometrically frustrated spin systems. We take an example in the Kagome-lattice anti-ferromagnets, and briefly review µSR works on S = 1, 3/2, and 5/2 Kagome compounds. PACS No.: 75.30

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