Spin Josephson effect in ferromagnet/ferromagnet tunnel junctions

Nogueira, Flavio S.; Bennemann, K. H.

doi:10.1209/epl/i2003-10305-x

Cited by 68 publications

(118 citation statements)

References 33 publications

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“…[21][22][23] The spin quantum axis is taken as the magnetic moment direction of the left FM lead h L (0,0,1) and the magnetic moment in the right FM lead is same as that in the last subsection h R (sin θ cos φ, sin θ sin φ, cos θ). Using the Green's function (Eq.…”

Section: Fm/fmmentioning

confidence: 99%

“…For the FM/FM tunnelling junction, a spontaneous ESC has been verified [20][21][22][23] flowing across the interface when the two magnetic moments h l and h r in the two leads of the junction are not collinear, and their exchange interaction determines the ESC J s , J s ∼ h l × h r . This indicates non-collinear magnetizations in the two leads can lead to spin flip and consequently a ESC through the junction.…”

Section: Introductionmentioning

confidence: 99%

“…This indicates non-collinear magnetizations in the two leads can lead to spin flip and consequently a ESC through the junction. Nogueira et al 22 and Lee et al 23 referred to the ESC through the FM/FM junction as the spin supercurrent as an analogy to the Josephson effect in superconductor junctions. The spin current in a FM/FM junction was also shown to result in magnetic moment reversal in one of the FM leads of the junction.…”

Section: Introductionmentioning

confidence: 99%

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Equilibrium spin current through tunneling junctions

Wang

Chan

2006

Phys. Rev. B

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We study equilibrium pure spin current through tunnelling junctions at zero bias. The two leads of the junctions connected via a thin insulator barrier, can be either a ferromagnetic metal (FM) or a nonmagnetic high-mobility twodimensional electron gas (2DEG) with Rashba spin orbital interaction (RSOI) or Dresselhaus spin orbital interaction (DSOI). As a lead of a tunnelling junction, the isotropic RSOI or DSOI in 2DEG can give rise to an average effective planar magnetic field orthogonal or parallel to the current direction. It is found by the linear response theory that equilibrium spin current J can flow in the following three junctions, 2DEG/2DEG, 2DEG/FM, and FM/FM junctions, as a result of the exchange coupling between the magnetic moments, h l and hr, in the two electrodes of the junction, i.e., J ∼ h l × hr. An important distinction between the FM and 2DEG with RSOI (DSOI) lead is that in a strict one-dimensional case RSOI (DSOI) cannot lead to equilibrium spin current in the junction since the two spin bands are not spin-polarized as in a FM lead where Zeeman spin splitting occurs.Pacs numbers: 72.25.Dc, 71.70. Ej

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Section: Fm/fmmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Equilibrium spin current through tunneling junctions

Wang

Chan

2006

Phys. Rev. B

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“…2(c), µ z R is plotted as a function of system length, L. For small system sizes, µ z R is independent of L, as in the SSF Eqs. (1) and (2). For intermediate film sizes, the dynamic dipole field dominates the exchange interaction.…”

mentioning

confidence: 99%

“…It has been suggested that certain ferromagnets may exhibit spin superfluidity (SSF) [1][2][3]. The superfluid spin-drag properties induced by spin transfer and spin pumping (SP) in a normal metal-ferromagnetnormal metal system have recently been computed [4][5][6].…”

mentioning

confidence: 99%

Spin Superfluidity and Long-Range Transport in Thin-Film Ferromagnets

2015

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In ferromagnets, magnons may condense into a single quantum state. Analogous to superconductors, this quantum state may support transport without dissipation. Recent works suggest that longitudinal spin transport through a thin-film ferromagnet is an example of spin superfluidity. Although intriguing, this tantalizing picture ignores long-range dipole interactions; we demonstrate that such interactions dramatically affect spin transport. In single-film ferromagnets, "spin superfluidity" only exists at length scales (a few hundred nanometers in yttrium iron garnet) somewhat larger than the exchange length. Over longer distances, dipolar interactions destroy spin superfluidity. Nevertheless, we predict re-emergence of spin superfluidity in tri-layer ferromagnet-normal metal-ferromagnet films of ∼ 1 µm in size. Such systems also exhibit other types of long-range spin transport in samples several micrometers in size.When matter enters a superfluid phase, it behaves like a fluid with zero viscosity and can support currents without dissipation. It has been suggested that certain ferromagnets may exhibit spin superfluidity (SSF) [1][2][3]. The superfluid spin-drag properties induced by spin transfer and spin pumping (SP) in a normal metal-ferromagnetnormal metal system have recently been computed [4][5][6]. Related studies have also explored Josephson spin currents between magnons condensates [7]. Experimental studies have suggested that the temporal decrease of magnon condensates is associated with SSF [8].In the absence of magnetic fields, SSF is indeed an intriguing possibility because its realization would allow spin currents to propagate without significant losses over long distances. These spin transport properties may be useful for low-dissipation interconnects, spin logic devices, and non-volatile magnetic memory devices. Our work demonstrates that SSF can exist in thin-film ferromagnetic systems, but two ferromagnets (rather than one) are required to cancel long-range dipole interactions. We do not observe signatures of long-range SSF in singlefilm ferromagnets.Recent works have hypothesized that easy-plane ferromagnetic thin films exhibit SSF. In such systems, a monotonously precessing magnetization leads to metastable spin-current-carrying states whose topological properties protect against dissipation [3]. Spin relaxation induces a finite resistance proportional to the system size [4]. Nevertheless, ferromagnetic insulators (FIs) have exceptionally low spin dissipation rates, and the spin supercurrent decays over a large length scale. Furthermore, the spin-relaxation-induced algebraic decay of the spin supercurrent significantly differs from the exponential decay of the spin current carried by spin waves [9]. Although magnetic anisotropy destroys the linear SSF response, the spin current is predicted to flow with negligible dissipation when the bias is sufficiently large [4,5].It is well known that long-range dipole interactions dramatically affect the spin-wave dispersion in thin films [10,11]. Low-energy ...

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Ultra-fast dynamics in solids: non-equilibrium behaviour of magnetism and atomic structure

Bennemann

2009

Ann. Phys.

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Spin Josephson effect in ferromagnet/ferromagnet tunnel junctions

Cited by 68 publications

References 33 publications

Equilibrium spin current through tunneling junctions

Equilibrium spin current through tunneling junctions

Spin Superfluidity and Long-Range Transport in Thin-Film Ferromagnets

Ultra-fast dynamics in solids: non-equilibrium behaviour of magnetism and atomic structure

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