Thermally driven spin injection from a ferromagnet into a non-magnetic metal

Slachter, A.; Bakker, F. L.; Adam, Jean-Paul; Wees, B. J. van

doi:10.1038/nphys1767

Cited by 411 publications

(439 citation statements)

References 31 publications

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“…As shown in Figure 3e, by fitting the diffusion function to the interval dependence of the thermal spin signal, which is defined as DR 2f s ¼ DV 2 s =I 2 , with the COMSOL simulation results (rT F ¼ 64 K mm À1 , I ¼ 0.78 mA), we obtained À72.1 mV K À1 as the spin-dependent Seebeck coefficient for the CFA (see Supplementary Information). This value is B20 times larger than the previously reported value in Slachter et al, 7 which implies that our CFA is a highly efficient thermal spin generator.…”

Section: Resultscontrasting

confidence: 52%

“…From a numerical simulation based on COMSOL, a large temperature gradient around the interface was effectively produced by the large current flow in the ferromagnetic injector, as shown in Figure 3b. 7,27 Because of the low resistivity of Cu, a partial current flowing in the ferromagnetic injector was injected into the Cu around the junction, which might contribute to the spin accumulation using electrical spin injection. However, such contributions were excluded using the secondharmonic lock-in technique.…”

Section: Resultsmentioning

confidence: 99%

“…Therefore, the generation efficiency of the spin current cannot exceed 100% even when a fully spin-polarized material, that is, a half-metal, is used. Furthermore, the spin current induced by thermal spin injection is determined by the difference in the Seebeck coefficient between the up and down spins, 7,15 which is known as the spin-dependent Seebeck effect. This effect is different from the spin Seebeck effect, 6,14 although both effects produce spin current and spin accumulation from the temperature gradient.…”

Section: Introductionmentioning

confidence: 99%

“…[6][7][8][9][10][11][12][13][14] A representative and fascinating phenomenon is thermal spin injection, in which excess heat can be used to produce spin current because of the spin-dependent Seebeck coefficient. [7][8][9] Until now, thermally driven spin injection has only been demonstrated using conventional ferromagnetic metals such as permalloy (Py) 7 and cobalt. 13 However, thermally excited spin current can only generate a few tens of nV which is low, because of the low spin-dependent Seebeck coefficient of conventional ferromagnetic metals.…”

Section: Introductionmentioning

confidence: 99%

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Efficient thermal spin injection using CoFeAl nanowire

Itoh

Kimura

2014

NPG Asia Mater

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Nanoelectronic devices based on electron spin can overcome the physical limitations of the present semiconductor technology because of their low power consumption while exploiting the spin degree of freedom of electrons. Although enhancing the efficiency of generation of the spin current is imperative and a primary issue for the practical application of spin-based electronics, seamless device integration with the conventional complementary metal-oxide semiconductor technology is another important milestone for developing spin-based nanoelectronics. In particular, the preparation of nanosized, magnetic, multilayered structures with electrical connections to individual complementary metal-oxide semiconductor circuits significantly complicates the fabrication procedure of nanoelectronic devices. Thermal spin injection, which is a recently discovered unique characteristic of spin current, may be an innovative method for simplifying device integration without the need for electricity, namely wireless spintronics. However, the feasibility of using the thermal spin injection method is poor because of its extremely low-generation efficiency. Here, we demonstrate that a highly spin-polarized, ferromagnetic CoFeAl electrode with a favorable band structure has excellent properties for thermal spin injection. The spin-dependent Seebeck coefficient is approximately 70 lV K À1 , which facilitates highly efficient generation of the spin current from heat. The heat generates approximately 100 times more spin voltage than a conventional ferromagnetic injector at room temperature. This innovative demonstration may open a new route for spin-device integration and its applications.

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Section: Resultscontrasting

confidence: 52%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Efficient thermal spin injection using CoFeAl nanowire

Itoh

Kimura

2014

NPG Asia Mater

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“…Our first-principles calculations reveal that this arises from a significantly enhanced Berry curvature associated with Weyl points near the Fermi energy 11 . As this e ect is geometrically convenient for thermoelectric power generation-it enables a lateral configuration of modules to cover a heat source 6 -these observations suggest that a new class of thermoelectric materials could be developed that exploit topological magnets to fabricate e cient, densely integrated thermopiles.Current intensive studies on thermally induced electron transport in ferromagnetic materials have opened various avenues for research on thermoelectricity and its application [12][13][14][15] . This trend has also triggered renewed interest in the anomalous Nernst effect (ANE) in ferromagnetic metals [3][4][5][6][7]15 , which is the spontaneous transverse voltage drop induced by heat current and is known to be proportional to magnetization (Fig.…”

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confidence: 99%

Large anomalous Nernst effect at room temperature in a chiral antiferromagnet

et al. 2017

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A temperature gradient in a ferromagnetic conductor can generate a transverse voltage drop perpendicular to both the magnetization and heat current. This anomalous Nernst e ect has been considered to be proportional to the magnetization 1-7 , and thus observed only in ferromagnets. Theoretically, however, the anomalous Nernst e ect provides a measure of the Berry curvature at the Fermi energy 8,9 , and so may be seen in magnets with no net magnetization. Here, we report the observation of a large anomalous Nernst e ect in the chiral antiferromagnet Mn 3 Sn (ref. 10). Despite a very small magnetization ∼0.002 µ B per Mn, the transverse Seebeck coe cient at zero magnetic field is ∼0.35 µV K −1 at room temperature and reaches ∼0.6 µV K −1 at 200 K, which is comparable to the maximum value known for a ferromagnetic metal. Our first-principles calculations reveal that this arises from a significantly enhanced Berry curvature associated with Weyl points near the Fermi energy 11 . As this e ect is geometrically convenient for thermoelectric power generation-it enables a lateral configuration of modules to cover a heat source 6 -these observations suggest that a new class of thermoelectric materials could be developed that exploit topological magnets to fabricate e cient, densely integrated thermopiles.Current intensive studies on thermally induced electron transport in ferromagnetic materials have opened various avenues for research on thermoelectricity and its application [12][13][14][15] . This trend has also triggered renewed interest in the anomalous Nernst effect (ANE) in ferromagnetic metals [3][4][5][6][7]15 , which is the spontaneous transverse voltage drop induced by heat current and is known to be proportional to magnetization (Fig. 1a). On the other hand, the recent Berry phase formulation of the transport properties has led to the discovery that a large anomalous Hall effect (AHE) may arise not only in ferromagnets, but in antiferromagnets and spin liquids, in which the magnetization is vanishingly small 10, [16][17][18][19][20][21][22] . As the first case in antiferromagnets, Mn 3 Sn has been experimentally found to exhibit a large AHE 10 . While the AHE is obtained by an integration of the Berry curvature for all of the occupied bands, the ANE is determined by the Berry curvature at E F (refs 8,9). Thus, the observation of a large AHE does not guarantee the observation of a large ANE. Furthermore, the ANE measurement should be highly useful to clarify the Berry curvature spectra near E F and to verify the possibility of the Weyl metal recently proposed for Mn 3 Sn (ref. 11).Mn 3 Sn has a hexagonal crystal structure with a space group of P6 3 /mmc (ref. 23). Mn atoms form a breathing type of kagome lattice in the ab-plane (Fig. 1b), and the Mn triangles constituting the kagome lattice are stacked on top along the c axis forming a tube of face-sharing octahedra. On cooling below the Néel temperature of 430 K, Mn magnetic moments of ∼3µ B lying in the ab-plane form a coplanar, chiral magnetic structure chara...

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