An anomalous Hall effect in altermagnetic ruthenium dioxide

Abstract

Anomalous Hall effect is a time-reversal symmetry breaking electronic response discovered in ferromagnets in the 19th century and continuing to play a key role in modern fields of physics and nanoelectronics. In contrast, the antiparallel magnetic order on common rutile crystals served as a classic example which kept compensated magnets for nearly a century outside the focus of the magneto-electronic research. Breaking with this traditional perception, the antiparallel magnetic order on the rutile crystal of RuO 2 has been predicted to generate anomalous Hall effect of comparable strength to ferromagnets. Here we report the experimental demonstration of the anomalous Hall effect in RuO 2 . We show that the effect arising from the antiparallel magnetic order dominates over an ordinary Hall contribution, and a contribution due to a weak field-induced magnetization. Our results open a prospect of research of relativistic topological Berry phases and dissipationless quantum transport in crystals of abundant elements and with a compensated antiparallel magnetic ordering at ambient conditions.

Significant Unconventional Anomalous Hall Effect in Heavy Metal/Antiferromagnetic Insulator Heterostructures

“…Three mechanisms cause the conventional AHE: intrinsic contribution by the Berry phase and extrinsic contributions by skew scattering and side jump. [40,41] In this study, such an AHE in the heterostructure system occurs owing to the interaction between the spin current (SHE in HM) and the magnetic structure (magnetic insulator, in this case, AFMI). Recently, it has been reported that an AFM topological spin texture emerges around the phase-transition temperature of Pt/α-Fe 2 O 3 heterostructures.…”

Significant Unconventional Anomalous Hall Effect in Heavy Metal/Antiferromagnetic Insulator Heterostructures

“…Three mechanisms cause the conventional AHE: intrinsic contribution by the Berry phase and extrinsic contributions by skew scattering and side jump. [ 40,41 ] In this study, such an AHE in the heterostructure system occurs owing to the interaction between the spin current (SHE in HM) and the magnetic structure (magnetic insulator, in this case, AFMI). Recently, it has been reported that an AFM topological spin texture emerges around the phase‐transition temperature of Pt/ α ‐Fe 2 O 3 heterostructures.…”

Inverse Altermagnetic Spin Splitting Effect‐Induced Terahertz Emission in RuO2

“…[15][16][17][18] The crystal structure and Néel vector of AFM provide a unique opportunity for tailoring the THz emission. [19,20] Recently, the altermagnetic materials with collinear compensated magnetic order and crystal rotation symmetry have been demonstrated to show strong time-reversal (T) symmetrybreaking responses, [21][22][23][24][25][26] such as the anomalous Hall effect [27][28][29] and the non-trivial spin current generation, [30][31][32][33][34] which are ascribed to the nonrelativistic altermagnetic spin splitting effect (ASSE). As a typical representative of altermagnetisms, the rutile RuO 2 possesses large spin splitting strength (≈1.4 eV [21] ), high conductivity (≈35 μΩcm [35] ) and high Néel temperature (above 300 K [36,37] ), attracting continuous attention for the application in spintronic devices.…”