Role of Interface Transparency and Exchange Field in the Superconducting Triplet Spin-Valve Effect

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

doi:10.4028/www.scientific.net/ssp.233-234.745

Cited by 8 publications

(4 citation statements)

References 8 publications

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“…The theoretical approach that we employ for the analysis of the experiment in Fig. 3 is based on a generalization of [12] along the lines of [27–28]. It allows to consider layered structures with different material parameters of all the layers and arbitrary Kupriyanov–Lukichev boundary parameters [29] of all the interfaces.…”

Section: Discussionmentioning

confidence: 99%

Superconducting switching due to a triplet component in the Pb/Cu/Ni/Cu/Co₂Cr₁_−xFe_xAl_y spin-valve structure

Kamashev¹,

Garif’yanov²,

Validov³

et al. 2019

Beilstein J. Nanotechnol.

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We report the superconducting properties of the Co2Cr1 −x Fe x Al y /Cu/Ni/Cu/Pb spin-valve structure the magnetic part of which comprises the Heusler alloy layer HA = Co2Cr1 −x Fe x Al y with a high degree of spin polarization (DSP) of the conduction band and a Ni layer of variable thickness. The separation between the superconducting transition curves measured for the parallel (α = 0°) and perpendicular (α = 90°) orientation of the magnetization of the HA and the Ni layers reaches up to 0.5 K (α is the angle between the magnetization of two ferromagnetic layers). For all studied samples the dependence of the superconducting transition temperature T c on α demonstrates a deep minimum in the vicinity of the perpendicular configuration of the magnetizations. This suggests that the observed minimum and the corresponding full switching effect of the spin valve is caused by the long-range triplet component of the superconducting condensate in the multilayer. Such a large effect can be attributed to a half-metallic nature of the HA layer, which in the orthogonal configuration efficiently draws off the spin-polarized Cooper pairs from the space between the HA and Ni layers. Our results indicate a significant potential of the concept of a superconducting spin-valve multilayer comprising a half-metallic ferromagnet, recently proposed by A. Singh et al., Phys. Rev. X 2015, 5, 021019, in achieving large values of the switching effect.

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Section: Discussionmentioning

confidence: 99%

Superconducting switching due to a triplet component in the Pb/Cu/Ni/Cu/Co₂Cr₁_−xFe_xAl_y spin-valve structure

Kamashev¹,

Garif’yanov²,

Validov³

et al. 2019

Beilstein J. Nanotechnol.

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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.…”

mentioning

confidence: 57%

“…Up to now, the role of the microscopic structure of the superconducting layer in S/F and S/F1/F2 proximity effects has received little attention from both theoretical and experimental researchers. Recent theories on S/F1/F2 proximity [5][6][7] treat the S layer as a flat and continuous layer without any more detailed discussion. Thus, in this work, we demonstrate experimentally that a significant cause of the small magnitude of the SSVE in metallic S/F1/F2 heterostructures is the rough surface of an S layer composed of overlapping islands, which can reduce ΔTc to zero.…”

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confidence: 99%

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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“…In the theory proposed by Fominov et al [9], the F-layers were represented by weak ferromagnets, whereas permalloy is not ferromagnetic. In addition, we ignored the limitation of the transparency of the Py1/Cu/Py2 interface, as was done in the theoretical studies of Deminov et al [21,22], because, in our case, this parameter would be free. In contrast to the parameters characterizing the transparency of the Py2/Pb interface, we cannot estimate this quantity from the experiment.…”

Section: Discussion Of Experimental Resultsmentioning

confidence: 99%

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

et al. 2018

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Abstract. In the present work we have studied the proximity-induced superconducting triplet pairing in CoO x /Py1/Cu/Py2/Cu/Pb spin-valve structure (where Py = Ni 0.81 Fe 0.19 ).For CoO x (3 nm)/Py(3 nm)/Cu(4 nm)/Py(0.6 nm)/Cu(2 nm)/Pb(70 nm) we have studied the dependence of the T c on the angle α between the direction of the cooling field and the external field both applied in the plane of the sample. We obtained that the T c does not change monotonically with the angle but passes through a minimum. To observe an "isolated" triplet spin-valve effect we exploited the oscillatory feature of the magnitude of the ordinary spin-valve effect ∆T c in the dependence of the Py2-layer thickness d Py2 . We determined the value of d Py2 at which ∆T c caused by the ordinary spin-valve effect is suppressed. This means that the difference in the T c between the antiparallel and parallel mutual orientation of magnetizations of the Py1 and Py2 layers is zero. For such a sample a "pure" triplet spin-valve effect which causes the minimum in T c at the orthogonal configuration of magnetizations has been observed.

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Role of Interface Transparency and Exchange Field in the Superconducting Triplet Spin-Valve Effect

Cited by 8 publications

References 8 publications

Superconducting switching due to a triplet component in the Pb/Cu/Ni/Cu/Co₂Cr₁_−xFe_xAl_y spin-valve structure

Superconducting switching due to a triplet component in the Pb/Cu/Ni/Cu/Co₂Cr₁_−xFe_xAl_y spin-valve structure

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

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

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Role of Interface Transparency and Exchange Field in the Superconducting Triplet Spin-Valve Effect

Cited by 8 publications

References 8 publications

Superconducting switching due to a triplet component in the Pb/Cu/Ni/Cu/Co2Cr1−xFexAly spin-valve structure

Superconducting switching due to a triplet component in the Pb/Cu/Ni/Cu/Co2Cr1−xFexAly spin-valve structure

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

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

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Superconducting switching due to a triplet component in the Pb/Cu/Ni/Cu/Co₂Cr₁_−xFe_xAl_y spin-valve structure

Superconducting switching due to a triplet component in the Pb/Cu/Ni/Cu/Co₂Cr₁_−xFe_xAl_y spin-valve structure