Antiferromagnetic superconductors

Buzdin, A. I.; Bulaevskiǐ, L. N.

doi:10.1070/pu1986v029n05abeh003375

Cited by 81 publications

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“…From Eq. (8) we see that magnetic moments renormalize the London penetration length so that the effective penetration length in magnetic superconductors is given by [2] …”

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confidence: 98%

“…For a Neel antiferromagnetic state there is always magnetic gap in the spectrum due to the magnetic anisotropy slightly renormalized by superconducting screening of RKKY and dipole-dipole interactions [3]. Neither experimental nor theoretical information on the strength of magnetic anisotropy or the structure of excitations in these materials is available so far.…”

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confidence: 99%

“…Here ω M = µ 2 n M /(2 ) at µB ≪ k B T M , the density of magnetic ions is n M and their magnetic moment is µ, ω s (k) is the magnetically active spin wave dispersion renormalized by the superconductivity [3], while ν s is the relaxation rate of spin waves due to the interaction with phonons. Using Eqs.…”

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confidence: 99%

“…Thus all quantities describing the moving vortex lattice, i.e the magnetic field and supercurrents, have the dependence on the coordinates and time in the combination (r − vt). In the field interval B ≪ H c2 the magnetic field should be found from the London equations [2,9,10] …”

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Spectroscopy of Magnetic Excitations in Magnetic Superconductors Using Vortex Motion

Bulaevskiǐ

Hruška²,

Maley³

2005

Phys. Rev. Lett.

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In magnetic superconductors a moving vortex lattice is accompanied by an ac magnetic field which leads to the generation of spin waves. At resonance conditions the dynamics of vortices in magnetic superconductors changes drastically, resulting in strong peaks in the dc I-V characteristics at voltages at which the washboard frequency of vortex lattice matches the spin wave frequency ωs(g), where g are the reciprocal vortex lattice vectors. We show that if washboard frequency lies above the magnetic gap, peaks in the I-V characteristics in borocarbides and cuprate layered magnetic superconductors are strong enough to be observed over the background determined by the quasiparticles.The coexistence of magnetism and superconductivity was observed in many crystals, such as RMo 6 S 8 , RRh 4 B 4 , RBa 2 Cu 3 O 7−δ and (R,A)CuO 4−δ (A=Sr, Ce) with the temperatures of magnetic ordering T M much smaller than the superconducting critical temperature T c , and also in borocarbides RT 2 B 2 C and ruthenocuprate RuSr 2 GdCu 2 O 8 with T M of the same order as T c . Here R is the rare earth element, while T=Ni, Ru, Pd, Pt. In such crystals f -electrons of ions R give rise to localized magnetic moments, while conducting electrons exhibit the Cooper pairing. In all these crystals, except HoMo 6 S 8 and ErRh 4 B 4 , magnetic moments order antiferromagnetically below T M . Such magnetic ordering coexists with superconductivity without strong interference because spin density varies on the scale much smaller than the superconducting correlation length and net magnetic moment vanishes, for review see Refs. 1, 2, 3.In this Letter we consider interplay between magnetic and superconducting excitations in magnetic superconductors, particularly interaction between a moving vortex lattice and spin waves via the ac magnetic field induced by moving vortices. The energy transfer from vortices to the magnetic system leads to dissipation which is additional to that caused by quasiparticles. This results in strong current peaks in the dc I-V characteristics at voltages at which the washboard frequency of vortex lattice [4] matches the spin wave frequency ω s (k) and k matches a reciprocal vortex lattice vector g.First we consider slightly anisotropic superconductors, i.e. all systems mentioned above except SmLa 1−x Sr x CuO 4−δ and RuSr 2 GdCu 2 O 8 crystals, and probably also Sm 2−x Ce x CuO 4−δ .The latter are layered superconductors with intrinsic Josephson junctions [5,6,7,8].We assume, for simplicity, a uniaxial crystal structure with the principal axis along z. The dc magnetic field is applied along the z-axis and we assume that the magnetic induction B(r), r = x, y, inside the superconductor corresponds to the ideal Abrikosov square vortex lattice (such a lattice is realized in clean borocarbide crystals in field B c in some field intervals [1]). The sublattice magnetization in the case of antiferromagnetic ordering is assumed to be oriented in the (x, y) plane. The dc transport current with the density j is along the y-axis which, due t...

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“…From Eq. (8) we see that magnetic moments renormalize the London penetration length so that the effective penetration length in magnetic superconductors is given by [2] …”

mentioning

confidence: 98%

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Spectroscopy of Magnetic Excitations in Magnetic Superconductors Using Vortex Motion

Bulaevskiǐ

Hruška²,

Maley³

2005

Phys. Rev. Lett.

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“…The topic of the interplay between antiferromagnetism and superconductivity has been extensively investigated [28][29][30][31][32]. Many of the "classic" antiferromagnetic superconductors like the Rhodium Boride cluster compounds and RMo 8 S 8 (R = Rare Earth) are well known to undergo field induced spin-flop transitions in the superconducting state which have been investigated both experimentally [33] and theoretically [34,35].…”

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Magnetoelectrodynamics at high frequencies in the antiferromagnetic and superconducting states ofDyNi2B2C

et al. 1998

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We report the observation of novel behaviour in the radio frequency (rf ) and microwave response of DyNi2B2C over a wide range of temperature (T ) and magnetic field (H) in the antiferromagnetic (AFM) and superconducting (SC) states. At microwave frequencies of 10 GHz, the T dependence of the surface impedance Zs = Rs + iXs was measured which yields the T dependence of the complex conductivity σ1 − iσ2 in the SC and AFM states. At radio frequencies (4 MHz), the H and T dependence of the penetration depth λ(T, H) were measured.The establishment of antiferromagnetic order at TN = 10.3 K results in a marked decrease in the scattering of charge carriers, leading to sharp decreases in Rs and Xs. However, Rs and Xs differ from each other in the AFM state. We show that the results are consistent with conductivity relaxation whence the scattering rate becomes comparable to the microwave frequency.The rf measurements yield a rich dependence of the scattering on the magnetic field near and below TN . Anomalous decrease of scattering at moderate applied fields is observed at temperatures near and above TN , and arises due to a crossover from a negative magnetoresistance state, possibly associated with a loss of spin disorder scattering at low fields, to a positive magnetoresistance state associated with the metallic nature. The normal state magnetoresistance is positive at all temperatures for µ0H > 2T and at all fields for T > 15K. Several characteristic field and temperature scales associated with metamagnetic transitions (HM1(T ), HM2(T )) and onset of spin disorder HD(T ), in addition to Tc, TN and Hc2(T ) are observed in the rf measurements.74.25. Ha, 74.25.Nf, 74.72.Ny, 75.20.Hr, 75.40.Gb, 75.50.Ee, 75.90.+w

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Magnetic Superconductors

Buzdin¹,

Flouquet²

2007

Handbook of Magnetism and Advanced Magnetic Materials

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We review the main mechanisms of the interplay between magnetism and superconductivity, and discuss first the properties of the conventional s‐wave antiferromagnetic and ferromagnetic superconductors. In the case of ferromagnetism, its antagonism with superconductivity leads to spectacular effects such as a reentrant superconductivity and the domain magnetic structure formation. It is now accepted that in heavy‐fermion compounds (HFCs) the superconductivity is unconventional. Here we analyze the ( P , T ) phase diagram with special focus on the stability of the different phases at T → 0 K. In the recently discovered ferromagnetic heavy‐fermion superconductors, the Cooper pairing appears to be a triplet. The studies of the properties of these compounds will certainly open a new chapter in the physics of superconductivity. We also discuss the particularities of the proximity effect in superconductor–ferromagnet heterostructures: the damped oscillatory behavior of the Cooper pair wave function and the conditions for the novel π‐Josephson junctions formation, which open an interesting perspective for the potential applications of these structures.

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Antiferromagnetic superconductors

Cited by 81 publications

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Spectroscopy of Magnetic Excitations in Magnetic Superconductors Using Vortex Motion

Spectroscopy of Magnetic Excitations in Magnetic Superconductors Using Vortex Motion

Magnetoelectrodynamics at high frequencies in the antiferromagnetic and superconducting states ofDyNi2B2C

Magnetic Superconductors

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