Giant Anomalous Hall Conductivity at the Pt/Cr ₂ O ₃ Interface

Abstract

The interface between a magnetic material and a heavy metal that has a large spin-orbit interaction is at the root of various spin-related phenomena. In this paper, we address the peculiar spin-dependent transport at a Pt/Cr 2 O 3 interface by exploring the origin of the nonlinear anomalous Hall effect (AHE) in Pt/Cr 2 O 3 bilayers. X-ray magnetic circular dichroism (XMCD) measurements show no appreciable magnetic moment at the interface originating from Cr 3d and Pt 5d orbitals, which could be associated with the AHE response. A possible interfacial magnetic moment M at the Pt/Cr 2 O 3 interface, assumed from the detection limit of the XMCD measurements, yields an anomalous Hall conductivity (σ AHE) per unit net magnetic moment (M ), −σ AHE /M, of 0.57 V −1 , which is extraordinary large compared with that for general magnetic materials. Together with first-principles calculations, the results suggest the possibility of an intrinsic AHE in the Pt/Cr 2 O 3 interface that does not rely on the net magnetic moment.

Voltage controlled Néel vector rotation in zero magnetic field

“…The Hall-like signal V xy is widely believed to originate from spin Hall magnetoresistance due to the fact that the mixing conductance has a non-zero imaginary component 31 , 33 . Potential additional contributions might originate from the anomalous Hall effect caused by magnetization which is proximity induced in the heavy metal Hall bar by the exchange field of the boundary magnetization or by anomalous Hall effect generated by spin chirality 32 , 34 . Regardless of the details of the mechanisms generating V xy , it has been experimentally established that V xy is a reliable proxy for the orientation of AFM boundary magnetization 30 , 31 , 35 .…”

Evidencing the formation of Pt nano-islands on Cr2O3/Ag(111)

“…5,6 The Pt/Cr 2 O 3 system has received growing attention lately since it was found to be a promising material for both catalytic and magnetic property investigations. [30][31][32][33][34][35] Kasikov et al 30 performed the deposition of Pt islands on Cr 2 O 3 followed by exposure to H 2 and CO diluted in synthetic air and heating at 723 K. The XPS spectra confirmed significant Pt 2+ and Pt 4+ chemical state contributions. After heating at 673 K in an ultra-high vacuum (UHV), an almost complete reduction of the platinum atoms to Pt 0 was achieved.…”

“…A spin Hall magnetoresistance effect was observed due to the paramagnetic Cr 2 O 3 . Moriyama et al 35 showed that Pt/Cr 2 O 3 yields an extremely large Hall conductivity per unit net magnetic moment if compared to the values of magnetic materials in general.…”

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

“…Heavy metal (HM)/antiferromagnetic (AFM) insulator (AFMI) heterostructures are an emerging essential system for investigating the interaction between spin current and antiferromagnetic (AFM) order, which have the potential for applications in energy-efficient, ultrafast, and robust spintronics devices. [1][2][3][4][5][6][7][8][9][10] In particular, the reflected spin current after interactions with the magnetic order at the interface can provide valuable information for determining the magnetic order, which has already been well established in the counterpart HM/ferromagnet (FM) heterostructures, such as the spin Hall magnetoresistance (SMR) and its derivative spin Hall-anomalous Hall effect (SH-AHE). [11,12] Most recently, considerable attention has been paid to SMR in HM/AFMI heterostructures, which is considered a probe for currentinduced switching of the AFM order.…”