Modulation of pure spin currents with a ferromagnetic insulator

Villamor, Estitxu; Isasa, Miren; Vélez, Saül; Bedoya-Pinto, Amílcar; Vavassori, P.; Hueso, Luis E.; Bergeret, F. S.; Casanova, Fèlix

doi:10.1103/physrevb.91.020403

Cited by 32 publications

(40 citation statements)

References 45 publications

(95 reference statements)

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“…As shown in Fig. S5(b) our simulation as described above reproduces the cos 2 (α) dependence observed in our experiments as well as by Villamor et al [16].…”

Section: Three Dimensional (3d) Spin Transport Modelsupporting

confidence: 89%

“…We also find that modifying the quality of the Al/YIG interface, using different thin-film deposition methods [4], influences G ↑↓ and hence the size of the spin current flowing at the Al/YIG interface. Recently, a low-temperature measurements of a similar effect was reported by Villamor et al [16] in Co/Cu devices where G ↑↓ ∼ 1011 Ω −1 m −2 was estimated, two orders of magnitude lower than in the literature [4,8]. Here, we present a room-temperature spintransport study in transparent Ni 80 Fe 20 (Py)/Al NLSV devices.…”

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confidence: 82%

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confidence: 57%

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Control of spin current by a magnetic YIG substrate in NiFe/Al nonlocal spin valves

et al. 2015

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We study the effect of a magnetic insulator (Yttrium Iron Garnet -YIG ) substrate on the spin transport properties of Ni80Fe20/Al nonlocal spin valve (NLSV) devices. The NLSV signal on the YIG substrate is about 2 to 3 times lower than that on a non magnetic SiO2 substrate, indicating that a significant fraction of the spin-current is absorbed at the Al/YIG interface. By measuring the NLSV signal for varying injector-to-detector distance and using a three dimensional spin-transport model that takes spin current absorption at the Al/YIG interface into account we obtain an effective spin-mixing conductance G ↑↓ 5 − 8 × 1013 Ω −1 m −2 . We also observe a small but clear modulation of the NLSV signal when rotating the YIG magnetization direction with respect to the fixed spin polarization of the spin accumulation in the Al. Spin relaxation due to thermal magnons or roughness of the YIG surface may be responsible for the observed small modulation of the NLSV signal.The coupled transport of spin, charge and heat in nonmagnetic (N) metals deposited on the magnetic insulator Y 3 Fe 5 O 12 (YIG) has led to new spin caloritronic device concepts such as thermally driven spin currents, the generation of spin angular momentum via the spin Seebeck effect (SSE) [1], spin pumping from YIG to metals [2], spin-orbit coupling (SOC) induced magnetoresistance effects [3,4] and the spin Peltier effect, i.e., the inverse of the SSE that describes cooling/heating by spin currents [5]. In these spin caloritronic phenomena, the spinmixing conductance G ↑↓ of the N/YIG interface controls the transfer of spins from the conduction electrons in N to the magnetic excitations (magnons) in the YIG, or vice versa [6][7][8][9][10]. The interconversion of spin current to a voltage employs the (inverse) spin Hall effect in heavymetals such as Pt or Pd. The possible presence of proximity induced magnetism in these metals is reported to introduce spurious magnetothermoelectric effects [11,12] or enhance G ↑↓ [7]. Owing to the short spin-diffusion length λ in these large SOC metals, the applicability of the diffusive spin-transport model is also questionable. Experimental measurements that alleviate these concerns are however scarce and hence are highly required.In this article, we investigate the interaction of spin current (in the absence of a charge current) with the YIG magnetization using the NLSV geometry [13][14][15]. Using a metal with low SOC and long spin-diffusion length allows to treat our experiment using the diffusive spin-transport model. We find that the NLSV signal on the YIG substrate is two to three times lower than that on the SiO 2 substrate, indicating significant spincurrent absorption at the Al/YIG interface. By varying the angle between the induced spin accumulation and the YIG magnetization direction we observe a small but clear modulation of the NLSV signal. We also find that modifying the quality of the Al/YIG interface, using different thin-film deposition methods [4], influences G ↑↓ and hence the size of the spin current...

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“…As shown in Fig. S5(b) our simulation as described above reproduces the cos 2 (α) dependence observed in our experiments as well as by Villamor et al [16].…”

Section: Three Dimensional (3d) Spin Transport Modelsupporting

confidence: 89%

supporting

confidence: 82%

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Control of spin current by a magnetic YIG substrate in NiFe/Al nonlocal spin valves

et al. 2015

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“…Given the interfacial origin of the effect, controlling the quality of the NM/FMI interface is crucial to get an enhanced magnetoresistance effect [27,28]. Although only recently discovered, the SMR has already proven to be a successful approach to quantify the spin-mixing interfacial conductance of NM/FMI bilayers [24,25,27,28], a concept at the base of this and other spin-dependent phenomena such as the spin Seebeck effect [29][30][31][32], the spin pumping [29,[33][34][35] or the magnetic gating of pure spin currents [36,37].…”

Section: Introductionmentioning

confidence: 99%

Spin Hall Magnetoresistance as a Probe for Surface Magnetization inPt/CoFe2O4Bilayers

et al. 2016

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We study the spin Hall magnetoresistance (SMR) in Pt grown in situ on CoFe 2 O 4 (CFO) ferrimagnetic insulating (FMI) films. A careful analysis of the angle-dependent and fielddependent longitudinal magnetoresistance indicates that the SMR contains a contribution that does not follow the bulk magnetization of CFO but it is a fingerprint of the complex magnetism at the surface of the CFO layer, thus signaling SMR as a tool for mapping surface magnetization. A systematic study of the SMR for different temperatures and CFO thicknesses gives us information impossible to obtain with any standard magnetometry technique. On one hand, surface magnetization behaves independently of the CFO thickness and does not saturate up to high fields, evidencing that the surface has its own anisotropy. On the other hand, characteristic zero-field magnetization steps are not present at the surface while they are relevant in the bulk, strongly suggesting that antiphase boundaries are the responsible of such intriguing features. In addition, a contribution from ordinary magnetoresistance of Pt is identified, which is only distinguishable due to the low resistivity of the in-situ grown Pt.

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“…One possible effect of B ROT is to tilt the Co magnetizations asymmetrically to reduce R NL . This effect is ruled out through anisotropic magnetoresistance measurements of the Co electrodes [34,35] striking feature is the similarity of all the curves, which show full modulation even for the lower applied magnetic fields. This indicates that the modulation is dominated by the proximity exchange field.…”

mentioning

confidence: 96%

Strong Modulation of Spin Currents in Bilayer Graphene by Static and Fluctuating Proximity Exchange Fields

et al. 2017

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Abstract:Two dimensional (2D) materials provide a unique platform to explore the full potential of magnetic proximity driven phenomena, which can be further used for applications in next generation spintronic devices. Of particular interest is to understand and control spin currents in graphene by the magnetic exchange field of a nearby ferromagnetic material in graphene/ferromagnetic-insulator (FMI) heterostructures. Here, we present the experimental study showing the strong modulation of spin currents in graphene layers by controlling the direction of the exchange field due to FMI magnetization. Owing to clean interfaces, a strong magnetic exchange coupling leads to the experimental observation of complete spin modulation at low externally applied magnetic fields in short graphene channels. Additionally, we discover that the graphene spin current can be fully dephased by randomly fluctuating exchange fields. This is manifested as an unusually strong temperature dependence of the non-local spin signals in graphene, which is due to spin relaxation by thermally-induced transverse fluctuations of the FMI magnetization. 2Use of the spin degree of freedom of electrons is poised to revolutionize next generation devices for logic [1] and memory [2] applications. Manipulation of spin current, using either a small electric or magnetic field, is the essential operation of such a device and is required to exploit the full versatility of spin related phenomena. Spins in graphene are of particular interest because of the fact that spins can propagate over large distances due to small spin-orbit (SO) coupling and negligible hyperfine interaction [3,4]. However, the absence of a strong SO field in graphene also means that spins in graphene cannot be manipulated by an external applied electric field [5]. In general, spins in graphene are manipulated by an out-of-plane magnetic field [6,7], known as Hanle spin precession, requiring large fields which are not viable for applications. An alternative route for efficient spin manipulation is to use the magnetic proximity effect of an adjacent ferromagnetic insulator (FMI). Two dimensional (2D) materials, like graphene, provide a unique platform to explore the proximity-induced phenomena as these effects are expected to be the strongest in 2D materials. There has been a great deal of interest to study the proximity effect induced changes in the electrical [8], optical [9,10] and spin [11] related properties of low dimensional materials. This research direction is further propelled by recent progress in the experimental techniques to assemble clean van der Waals heterostructures of 2D materials or mechanically transfer 2D samples onto arbitrary materials [12,13]. Recently, magnetic proximity effects in graphene/FMI heterostructures has been explored by charge transport measurements: (1) demonstration of ferromagnetism in graphene coupled to yttrium iron garnet (YIG), [14] and (2) large magnetic exchange fields experienced by charge carriers in graphene/EuS heterostructures [15...

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Modulation of pure spin currents with a ferromagnetic insulator

Cited by 32 publications

References 45 publications

Control of spin current by a magnetic YIG substrate in NiFe/Al nonlocal spin valves

Control of spin current by a magnetic YIG substrate in NiFe/Al nonlocal spin valves

Spin Hall Magnetoresistance as a Probe for Surface Magnetization inPt/CoFe2O4Bilayers

Strong Modulation of Spin Currents in Bilayer Graphene by Static and Fluctuating Proximity Exchange Fields

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