From Colossal to Zero: Controlling the Anomalous Hall Effect in Magnetic Heusler Compounds via Berry Curvature Design

Abstract

Since the discovery of the anomalous Hall effect (AHE), the anomalous Hall conductivity (AHC) has been thought to be zero when there is no net magnetization. However, the recently found relation between the intrinsic AHE and the Berry curvature predicts other possibilities, such as a large AHC in non-colinear antiferromagnets with no net magnetization but net Berry curvature.Vice versa, the AHE in principle could be tuned to zero, irrespective of a finite magnetization.Here, we experimentally investigate this possibility and demonstrate that, the symmetry elements of Heusler magnets can be changed such that the Berry curvature and all the associated properties are switched while leaving the magnetization unaffected. This enables us to tune the AHC from 0 Ω -1 cm -1 up to 1600 Ω -1 cm -1 with an exceptionally high anomalous Hall angle up to 12%, while keeping the magnetization same. Our study shows that the AHC can be controlled by selectively changing the Berry curvature distribution, independent of the magnetization. † Metallographic Characterization:The metallographic analysis was performed using an optical (Fig. S1) and a scanning probe electron (Fig. S2) microscopy for all the single crystals of Co2VGa (a), Co2MnGa (b) and Mn2CoGa (c). The samples are found to be single phase with homogeneous distribution of the chemical composition. The results of the compositional analysis with energy-dispersive X-ray (EDX) spectroscopy is summarized in table-S1. For the optical microscopy measurement, small crystals were embedded in epoxy resin blocks, and a smooth surface was prepared. In order to resolve the discrepancy between the theoretical calculation and the experimental Hall conductivity of the inverse Heusler compound Mn2CoGa, a detailed chemical analysis was performed. The chemical composition of the grown Mn2CoGa single crystals was determined as: Mn2.07Co1.04Ga confirming slight electron doping in the samples.

Intrinsic Anomalous Hall Effect in Ni-Substituted Magnetic Weyl Semimetal Co3Sn2S2

“…13 The layered Shandite compound Co3Sn2S2 is one of the very few known magnetic Weyl semimetals. [14][15][16] Apart from its interesting topological properties, this compound is also investigated for its thermoelectric properties and possible skyrmionic phase. 17 The topological effect evoked by the Weyl points is responsible for the giant anomalous Hall effect in this compound.…”

Prediction of ferroelectricity-driven Berry curvature enabling charge- and spin-controllable photocurrent in tin telluride monolayers

“…20,21 Since level crossing can generate a singular BC distribution, topological materials that possess small inverted band gaps or band crossings have been mostly studied as efficient platforms for hosting a large BC dipole. [20][21][22][23][24][25][26] For instance, a small-gap quantum spin Hall WTe2 monolayer shows a large inter-band BC and its dipole is manipulated by an external electric field, resulting in the circular photogalvanic effect. 20 Tilted Weyl semimetals and pressurized BiTeI that is driven towards the topological phase transition regime also exhibit a large enhancement in the intra-band BC dipole, leading to the nonlinear Hall effect by generating a transverse photocurrent under linearly polarized light.…”

“…As a result, the reversal of the photon helicity inverts the direction of the charge current only, remaining the spin current invariant. In addition to the time-dependent DFT calculations and the symmetry argument, we develop an analytic formalism for the charge and spin photogalvanic currents to verify their ferroelectric origin and the manoeuvrability by the photon handedness and the ferroelectricity [see Supplementary Eqs (21),(22),(24),. and(25)].…”

Magnetization-governed magnetoresistance anisotropy in the topological semimetal CeBi

“…extensively sought, leading to the recent revelation of magnetic topological insulator MnBi2Te4 [13][14][15][16][17][18][19][20]. Since 2016, researchers have also been searching for other types of topological materials with intrinsic magnetic order and uncovered a number of magnetic topological semimetals [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38], which may lead to topologically-driven spintronics [37] and have become a focus center in the field . Extensive exploration of these materials has led to the discovery of exotic properties.…”

“…For example, both axion insulator and Chern insulator states have been demonstrated in magnetic topological insulator MnBi2Te4 [20]. Magnetization driven giant nematic energy shift [27] and large intrinsic anomalous Hall effects were observed in magnetic topological semimetals [26,[29][30][31][32][33][34]. A new phenomenon called singular angular magnetoresistance is discovered in magnetic Weyl semimetal CeAlGe system very recently [39].…”