Anisotropic magnetoresistance and nontrivial spin Hall magnetoresistance in Pt/α−Fe2O3 bilayers

Abstract

To date, magnetic proximity effect (MPE) has only been conclusively observed in ferromagnet (FM) based systems. We report the observation of anomalous Hall effect and anisotropic magnetoresistance in angular dependent magnetoresistance (ADMR) measurements in Pt on antiferromagnetic (AF) α-Fe2O3(0001) epitaxial films at 10 K, which provide evidence for the MPE. The Néel order of α-Fe2O3 and the induced magnetization in Pt show a unique ADMR compared with all other FM and AF systems. A macrospin response model is established and can explain the AF spin configuration and all main ADMR features in the Pt/α-Fe2O3 bilayers.

Antiferromagnetic Magnon Drag Effect and Giant On–Off Ratio in a Vertical Device

“…SMR is carried out with current applied and voltage measured in the same Pt layer. [37,38] The comparison of the present AFM magnon drag effect and SMR shows two striking features: i) The polarity of SMR signal is opposite to that of AFM magnon drag effect, suggesting that the leakage current, if any, cannot result in the magnon drag signal. ii) The magnitude of SMR is at least six orders smaller than that of the AFM magnon drag effect, demonstrating the unique advantage of magnon drag during the read-out process in AFM.…”

“…In addition to the two specific positions, we plot in Figure 2e the voltage signals as a function of the in-plane rotation angle (𝛼) to further investigate the AFM magnon drag phenomenon. The applied magnetic field is 3 T, which is sufficiently strong to maintain the spin-flop state in all directions, [37,38] therefore currentinduced Néel vector switching should not exist. [39] A signal offset due to parasitic potential in Pt (measured at I b = 0, see Figure S3 in the Supporting Information) is subtracted so that the voltage signal is symmetrical about 0.…”

“…ii) The magnitude of SMR is at least six orders smaller than that of the AFM magnon drag effect, demonstrating the unique advantage of magnon drag during the read-out process in AFM. Previously, the detected onoff signals in AFM spintronics are normally below 0.01 based on SMR [37] or AMR, [5] and around 0.2 based on antiferromagnetferromagnet phase transition [14] or fragmented domain states. [40] This is caused by the concomitant electrical current and intrinsic nonvanishing off state signal.…”

“…In addition to rotating magnetic field within the xy-plane (𝛼), the experiments with H (of the same strength, 3 T) rotating in other two planes, yz-plane (𝛽) and xz-plane (𝛾), are also performed and depicted in Figure 2f. During the 𝛽-scan, V maintains minima at most of angle where the Néel vector is always at the spin-flop state and along x-axis, [37,38] resulting in the absence of magnon transport, which corresponds to 𝛼 = 90°/270°during 𝛼-scan. As for the 𝛾-scan, the situation differs dramatically.…”

Static magnetic proximity effects and spin Hall magnetoresistance in Pt/Y3Fe5O12 and inverted Geprägs1, Klewe2, Meyer3 et al. 2020Phys. Rev. B12040View full textAdd to dashboardCite

“…This characteristic angle dependence is inconsistent with the conventional AMR of a polycrystalline HM layer [32] and is, instead, explained by an interplay of charge and spin currents at the interface between the FMI and the HM layer via the (inverse) SHE [33]. This so-called spin Hall magnetoresistance (SMR) was further experimentally confirmed in a variety of HM/FMI heterostructures such as Pt/YIG [31,32,[34][35][36][37][38], Ta/YIG [35], Pt/Gd 3 Fe 5 O 12 [39], Pt/Fe 3 O 4 [32], Pt/NiFe 2 O 4 [32,40], Pt/CoFe 2 O 4 [41], and Pt/Cu 2 OSeO 3 [42] as well as using antiferromagnetic insulators NiO [43][44][45][46], Cr 2 O 3 [47,48], and α-Fe 2 O 3 [46,[49][50][51]. The exchange of spin angular momentum as the underlying mechanism of the SMR is further confirmed by Pt/YIG/Pt trilayer structures [52,53] and nonlocal transport experiments in Pt/YIG bilayer nanostructures [54][55][56].…”