Proximity effects in superconducting triplet spin-valve F2/F1/S

Деминов, Р. Г.; Тагиров, Л. Р.; Gaifullin, R.R.; Karminskaya, T. Yu.; Kupriyanov, M. Yu.; Fominov, Ya. V.; Golubov, A. A.

doi:10.1016/j.jmmm.2014.02.033

Cited by 21 publications

(19 citation statements)

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“…Nearly all of the past theoretical works on SF F structures have considered the diffusive case, [34][35][36][37][38] where impurities strongly scatter the quasiparticles. The clean regime has been studied, using a self-consistent solution of the Bogoliubovde Gennes (BdG) 39 equations, in Ref.…”

Section: Introductionmentioning

confidence: 99%

Zero-energy peak and triplet correlations in nanoscale superconductor/ferromagnet/ferromagnet spin valves

2015

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Using a self-consistent Bogoliubov-de Gennes approach, we theoretically study the proximity-induced density of states (DOS) in clean SF F spin-valves with noncollinear exchange fields. Our results clearly demonstrate a direct correlation between the presence of a zero energy peak (ZEP) in the DOS spectrum and the persistence of spin-1 triplet pair correlations. By systematically varying the geometrical and material parameters governing the spin-valve, we point out to experimentally optimal system configurations where the ZEPs are most pronounced, and which can be effectively probed via scanning tunneling microscopy. We complement these findings in the ballistic regime by employing the Usadel formalism in the full proximity limit to investigate their diffusive SF F counterparts. We determine the optimal normalized ferromagnetic layer thicknesses which result in the largest ZEPs. Our results can serve as guidelines in designing samples for future experiments.

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Section: Introductionmentioning

confidence: 99%

Zero-energy peak and triplet correlations in nanoscale superconductor/ferromagnet/ferromagnet spin valves

2015

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“…Here, we apply the method of Ref. [19] (extended to the case of arbitrary S/F interface transparency [25]) for direct fitting of our data on T c (α), as shown in Fig. 2(a) by a solid line.…”

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Isolation of proximity-induced triplet pairing channel in a superconductor/ferromagnet spin valve

et al. 2016

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We have studied the proximity-induced superconducting triplet pairing in CoOx/Py1/Cu/Py2/Cu/Pb spin-valve structure (where Py = Ni0.81Fe0.19).By optimizing the parameters of this structure we found a triplet-channel assisted full switching between the normal and superconducting states. To observe an "isolated" triplet spin-valve effect we exploited the oscillatory feature of the magnitude of the ordinary spin-valve effect ∆Tc in the dependence of the Py2-layer thickness dP y2. We determined the value of dP y2 at which ∆Tc caused by the ordinary spin-valve effect (the difference in the superconducting transition temperature Tc between the antiparallel and parallel mutual orientation of magnetizations of the Py1 and Py2 layers) is suppressed. For such a sample a "pure" triplet spin-valve effect which causes the minimum in Tc at the orthogonal configuration of magnetizations has been observed.The superconducting spin-valve effect consists of different degree of suppression of superconductivity in the F1/F2/S or F1/S/F2 thin film multilayer constructions at parallel (P) and antiparallel (AP) mutual orientation of magnetizations of the F1 and F2 ferromagnetic layers. The superconducting spin valves based on the superconductor/ferromagnet (S/F) proximity effect offer a playground to explore fundamental aspects of interplay between superconductivity and magnetism and also promise applications as passive devices of the superconducting spintronics. The latter construction should be operational upon application of a small external magnetic field. Many experimental works were performed to confirm this effect for the S/F systems with a good contact between metallic F and S layers made of ordinary metals and standard ferromagnets (see, e.g., recent reviews [6]), the full switching between the superconducting and normal states has been realized only in a few cases [7,8] because ∆T c was usually smaller than the width of the superconducting transition δT c .Very recently, Singh et al. reported [9] the observation of a colossal triplet spin-valve effect for the S/F1/N/F2 structure made of amorphous MoGe, Ni, Cu, and CrO 2 as the S, F1, N, and F2 layers, respectively. This structure demonstrated variation of T c by ∼ 1 K when changing the relative alignment of the two F layers. It was shown that the optimal operational field for this device is of the order of 20 kOe. Gu et al. [10,11] reported ∆T c ∼ 400 mK for Ho/Nb/Ho trilayers. Also in this case the parallel configuration of magnetizations was reached at a field of ∼ 10 kOe. The high operational fields of these spin valves are disadvantageous for the superconducting spintronics. Besides, the physical reasons for large values of ∆T c for spin valve based on half-metals are not yet theoretically explained. This calls for elaboration of classical spinvalve structures which use standard ferromagnets (Fe, Co, Ni) and their alloys with good electrical contacts between all layers and for which theoretical understanding of the operational principle is available.Oh et al. [12] propos...

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“…A similar theory for a F1/S/F2 multilayer was proposed in 1999 by Tagirov [3] and Buzdin et al [4]. Later, a triplet spin valve effect was described theoretically for S/F1/F2 structures by Fominov et al [5][6][7], who proposed another way to manipulate Tc, which is related to the formation of a long-range triplet component of the superconducting condensate at a non-collinear orientation of the F1 and F2 magnetizations.…”

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confidence: 58%

Boosting the superconducting spin valve effect in a metallic superconductor/ferromagnet heterostructure

et al. 2016

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Superconducting spin valves based on the superconductor/ferromagnet (S/F) proximity effect are considered to be a key element in the emerging field of superconducting spintronics. Here, we demonstrate the crucial role of the morphology of the superconducting layer in the operation of a multilayer S/F1/F2 spin valve. We study two types of superconducting spin valve heterostructures, with rough and with smooth superconducting layers, using transmission electron microscopy in combination with transport and magnetic characterization. We find that the quality of the S/F interface is not critical for the S/F proximity effect, as regards the suppression of the critical temperature of the S layer. However, it appears to be of paramount importance in the performance of the S/F1/F2 spin valve. As the morphology of the S layer changes from the form of overlapping islands to a smooth case, the magnitude of the conventional superconducting spin valve effect significantly increases. We attribute this dramatic effect to a homogenization of the Green function of the superconducting condensate over the S/F interface in the S/F1/F2 valve with a smooth surface of the S layer.It is well known that bringing together two antagonistic ordered states of matter, namely superconductivity (S) and ferromagnetism (F), in a thin S/F heterostructure gives rise to a variety of new physical phenomena, such as the S/F/S π-phase Josephson effect, the so-called cryptoferromagnetic state, conventional (singlet) and unconventional (triplet) superconducting spin valve effects (SSVE) (e.g., see a recent review [1] and references therein). The SSVE for a sequence of two metallic F layers and one S layer, S/F1/F2, was proposed theoretically in 1997 by Oh et al. [2]. This multilayer structure can be switched between the normal and superconducting states by changing the mutual orientations of the magnetizations of the F1 and F2 layers between parallel (P) and antiparallel (AP) configurations. The physical mechanism behind this effect involves manipulating the phase and amplitude of the superconducting wave function penetrating into the F1 layer and, hence, the superconducting critical temperature, Tc, by changing the magnetic state of the F1/F2 part of the heterostructure. A similar theory for a F1/S/F2 multilayer was proposed in 1999 by Tagirov [3] and Buzdin et al. [4]. Later, a triplet spin valve effect was described theoretically for S/F1/F2 structures by , who proposed another way to manipulate Tc, which is related to the formation of a long-range triplet component of the superconducting condensate at a non-collinear orientation of the F1 and F2 magnetizations.At present, there have been a number of experimental works confirming the SSVE (see, e.g.,

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Proximity effects in superconducting triplet spin-valve F2/F1/S

Cited by 21 publications

References 4 publications

Zero-energy peak and triplet correlations in nanoscale superconductor/ferromagnet/ferromagnet spin valves

Zero-energy peak and triplet correlations in nanoscale superconductor/ferromagnet/ferromagnet spin valves

Isolation of proximity-induced triplet pairing channel in a superconductor/ferromagnet spin valve

Boosting the superconducting spin valve effect in a metallic superconductor/ferromagnet heterostructure

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