Spin-Hall magnetoresistance and spin Seebeck effect in spin-spiral and paramagnetic phases of multiferroic<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mtext>CoCr</mml:mtext><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mtext>O</mml:mtext><mml:mn>4</mml:mn></mml:msub></mml:mrow></mml:math>films

Aqeel, Aisha; Vlietstra, N.; Heuver, J. A.; Bauer, G.; Noheda, Beatriz; Wees, B. J. van; Palstra, Thomas

doi:10.1103/physrevb.92.224410

Cited by 82 publications

(79 citation statements)

References 45 publications

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“…The InYGdIG/Pt sample clearly violates this conjecture, showing that the SMR is a powerful method to characterize complex spin textures. The small SMR modulation observed in CoCr 2 O 4 and Cu 2 OSeO 3 can thus indeed be evidence for different spin spiral phases [32,33].…”

Section: -4mentioning

confidence: 94%

Spin Hall magnetoresistance in a canted ferrimagnet

et al. 2016

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We study the spin Hall magnetoresistance effect in ferrimagnet/normal metal bilayers, comparing the response in collinear and canted magnetic phases. In the collinear magnetic phase, in which the sublattice magnetic moments are all aligned along the same axis, we observe the conventional spin Hall magnetoresistance. In contrast, in the canted phase, the magnetoresistance changes sign. Using atomistic spin simulations and x-ray absorption experiments, we can understand these observations in terms of the magnetic field and temperature dependent orientation of magnetic moments on different magnetic sublattices. This enables a magnetotransport based investigation of noncollinear magnetic textures. DOI: 10.1103/PhysRevB.94.094401The magnetic properties of ferromagnets are often modeled in terms of a simple macrospin with magnetization vector M. In this picture, one tacitly assumes that all individual atomic magnetic moments μ are aligned in one direction, such that the magnetization is M = nμ with the moment number density n. However, many magnets exhibit a much richer magnetic structure, with canted, spiral, frustrated, or even topological [1,2] phases appearing in addition to collinear magnetic order. Unravelling these experimentally typically requires sophisticated methods, e.g., spin polarized neutron scattering, x-ray magnetic circular dichroism, or Lorentz transmission electron microscopy. A pathway for the electrical detection of magnetic properties is provided by spin torques arising at a magnet/metal interface [3][4][5]. These torques govern fundamental spintronic phenomena such as spin pumping [6][7][8][9][10], spin Seebeck effect [11][12][13], as well as spin Hall magnetoresistance [14][15][16][17][18], and even enable an electrical control of the magnetization in magnetic nanostructures [3][4][5]. However, while the spin torque effect-or more precisely the transfer of spin angular momentum across the magnet/metal interface-has been extensively discussed for a macrospin M [19,20], the action of spin torques on noncollinear magnetic phases is only poorly understood.Here we show that in the ferrimagnet gadolinium iron garnet (Gd 3 Fe 5 O 12 , GdIG), the spin Hall magnetoresistance (SMR) can be used to resolve the orientation of magnetic moments residing on different magnetic sublattices. We thereby prove that the SMR is not just governed by the net moment μ net = μ (viz. the corresponding macrospin magnetization * Present address: Institut für Festkörperphysik, Technische Universität Dresden, D-01062 Dresden, Germany; goennenwein@ wmi.badw.de M net ) aligned along the externally applied magnetic field. This is reflected most conspicuously by the SMR sign inversion observed for canted sublattice moments. The interpretation of our experiments is corroborated by x-ray magnetic circular dichroism (XMCD) measurements, and atomistic spin simulations [13] suggesting that the Fe sublattice moments dominate the SMR response.The SMR originates from spin current transport across the interface between an (insulating) ma...

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Section: -4mentioning

confidence: 94%

Spin Hall magnetoresistance in a canted ferrimagnet

et al. 2016

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“…The SMR is an interface effect [4][5][6] , whereas the SSE is explained as a bulk effect in which thermal magnons play an important role 10-12 . The SMR and SSE can be used to detect magnetic states, as recently demonstrated for a frustrated magnet 22 . We performed a systematic study of the excitation and detection of spin currents in the spin spiral magnet CSO using the SMR and SSE in a transverse planar Hall-bar geometry.…”

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confidence: 99%

“…Here, we report the spin-Hall magnetoresistance (SMR) [1][2][3][4] sensitive to the surface magnetization [4][5][6] of the spin-spiral material, Cu 2 OSeO 3 . We experimentally demonstrate that the angular dependence of the SMR changes drastically at the transition between the helical spiral and the conical spiral phases.…”

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confidence: 99%

“…In the SMR, both the SHE and ISHE play a concerted role, whereas in the SSE, thermal gradients across an interface result in a magnonic spin current, detected electrically by the ISHE. The SMR is an interface effect [4][5][6] , whereas the SSE is explained as a bulk effect in which thermal magnons play an important role 10-12 . The SMR and SSE can be used to detect magnetic states, as recently demonstrated for a frustrated magnet 22 .…”

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Electrical detection of spiral spin structures inPt|Cu2OSeO3heterostructures

et al. 2016

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The interaction between the itinerant spins in metals and localized spins in magnetic insulators thus far has only been explored in collinear spinsystems, such as garnets. Here, we report the spin-Hall magnetoresistance (SMR) 1-4 sensitive to the surface magnetization 4-6 of the spin-spiral material, Cu 2 OSeO 3 . We experimentally demonstrate that the angular dependence of the SMR changes drastically at the transition between the helical spiral and the conical spiral phases. Furthermore, the sign and magnitude of the SMR in the conical spiral state are controlled by the cone angle. We show that this complex behaviour can be qualitatively explained within the SMR theory initially developed for collinear magnets. In addition, we studied the spin Seebeck effect (SSE) 7-9 , which is sensitive to the bulk magnetization [10][11][12] . It originates from the conversion of thermally excited low-energy spin waves in the magnet, known as magnons, into the spin current in the adjacent metal contact (Pt). The SSE displays unconventional behavior where not only the magnitude but also the phase of the SSE vary with the applied magnetic field.Cu 2 OSeO 3 (CSO) belongs to the family of cubic chiral magnets 13 , including MnSi, Fe 0.5 Co 0.5 Si and FeGe, in which magnetic skyrmions have been found recently 14 . Unlike the itinerant magnet MnSi, CSO is a ferrimagnetic Mott insulator with a band gap of 2.1 eV15 . Yet the magnetic phase diagram of CSO, showing a variety of non-collinear spin states (see Fig. 1a), is similar to those of other cubic chiral magnets. At low applied magnetic fields CSO is in an incommensurate helical spiral state with a long period of ∼50 nm 16 stabilized by the relativistic Dzyaloshinskii-Moriya interaction 17 . In this multi-domain state the spiral wave vector Q can be oriented along any of the three equivalent directions: [100], [010] or [001] 18 . Above the critical field, H c1 , a transition into a conical spiral state occurs, in which Q H. As the field increases, the cone angle θ becomes smaller. Eventually, θ becomes 0 at the second critical field, H c2 , which marks the transition to the field-induced collinear ferrimagnetic (FM) state. The evolution of the magnetic structure of CSO under an increasing magnetic field is depicted in Figs. 1b-g. Recently, the coupling of magnetization to spin, charge and heat currents was much studied in the context of next generation spintronic applications. In this development, the spin-Hall magnetoresistance (SMR) and spin Seebeck effect (SSE) are very prominent, as they provide information on the magnetization of an insulating magnetic layer by purely electrical measurements. The underlying physics of these phenomena hinges on the conversion between charge and transverse spin currents -the spin Hall effect (SHE) and its inverse (ISHE) 19-21 . In the SMR, both the SHE and ISHE play a concerted role, whereas in the SSE, thermal gradients across an interface result in a magnonic spin current, detected electrically by the ISHE. The SMR is an interface ef...

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“…This spin-current-induced magnetoresistance is now recognized as an indispensable tool for investigating the spin transport in ferromagnetic material=metal heterostructures. [16][17][18][19] The spin Hall magnetoresistance (SMR) refers to the resistance change due to the spin current generated by the spin Hall effect (SHE), which interacts with a ferromagnetic material. 4,6) Typically in materials consisting of heavy metals such as Pt and W, 4,9) a spin current is induced by an applied charge current, j c , due to the SHE.…”

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Spin-current-induced magnetoresistance in trilayer structure with nonmagnetic metallic interlayer

Iguchi

Sato

Uchida

et al. 2017

Jpn. J. Appl. Phys.

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We have theoretically investigated the spin Hall magnetoresistance (SMR) and Rashba-Edelstein magnetoresistance (REMR), mediated by spin currents, in a ferrimagnetic insulator/nonmagnetic metal/heavy metal system in the diffusive regime. The magnitude of both SMR and REMR decreases with increasing thickness of the interlayer because of the current shunting effect and the reduction in spin accumulation across the interlayer. The latter contribution is due to driving a spin current and persists even in the absence of spin relaxation, which is essential for understanding the magnetoresistance ratio in trilayer structures. © 2017 The Japan Society of Applied Physics M agnetoresistance effects are important for applications in sensor and memory devices and for investigation of spin-dependent transport. [1][2][3] Recently, a new type of magnetoresistance has been demonstrated, in which a spin current generated via spin-orbit coupling from an applied charge current plays a central role. [4][5][6][7][8][9][10][11][12] The generated spin current interacts with magnetization and magnetic field and changes its magnitude. 6,8,11,13) When the spin current is converted back to a charge current by spin-orbit coupling, 14,15) the spin-current transport modulates the conductivity of the system, and then gives rise to magnetoresistance. This spin-current-induced magnetoresistance is now recognized as an indispensable tool for investigating the spin transport in ferromagnetic material=metal heterostructures. [16][17][18][19] The spin Hall magnetoresistance (SMR) refers to the resistance change due to the spin current generated by the spin Hall effect (SHE), which interacts with a ferromagnetic material. 4,6) Typically in materials consisting of heavy metals such as Pt and W, 4,9) a spin current is induced by an applied charge current, j c , due to the SHE. This spin current propagates in the material and forms spin accumulation, s , around the system edges. 20) When s acts on a ferromagnetic material, it exerts spin transfer torque on the magnetization m, which is given by 13)Here, the spin current is defined to be positive when it flows out of the F layer, and e > 0, G r , m, and s j interface respectively denote the elementary charge, the real part of the mixing conductance per unit area, and the magnetization unit vector, the spin accumulation at the interface. Since j STT s is absorbed by the magnetization, the resultant spin accumulation s decreases, which results in the reduction in backflow spin current and thus the additional charge current due to the SHE (Fig. 1). As j STT s depends on the magnetization direction, the spin-current absorption finally appears as a magnetoresistance effect, under which the total conductivity σ shows a different dependence on m from the conventional anisotropic magnetoresistance, 6) i.e.,where n, σ 0 , and Δσ SMR respectively denote the unit vector normal to the junction interface and the conductivities insensitive and sensitive to the magnetization. In the context of SMR research, an interla...

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Spin-Hall magnetoresistance and spin Seebeck effect in spin-spiral and paramagnetic phases of multiferroicCoCr2O4films

Cited by 82 publications

References 45 publications

Spin Hall magnetoresistance in a canted ferrimagnet

Spin Hall magnetoresistance in a canted ferrimagnet

Electrical detection of spiral spin structures inPt|Cu2OSeO3heterostructures

Spin-current-induced magnetoresistance in trilayer structure with nonmagnetic metallic interlayer

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