Magnetic excitations of the 2-D Sm spin layers in

Ronning, F.; Capan, C.; Moreno, N. O.; Thompson, J. D.; Bulaevskiǐ, L. N.; Movshovich, R.; Marel, D. van der

doi:10.1016/j.jmmm.2006.10.366

Cited by 3 publications

(4 citation statements)

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“…The Josephson nature of the interlayer coupling in this crystal has been confirmed by observation of the double Josephson plasma resonance stemming from two layers in a unit cell [5]. The specific heat measurements [6] show that magnetic ordering is absent down to a temperature of 0.3 K and a magnetic gap, if any, lies below 0.3 K. They reveal also a broad peak near the temperature 1 K and the height of this peak indicates the presence of competing interactions that might be described by the two-dimensional J 1 -J 2 Heisenberg model with J 2 /J 1 > 0.4 [6,15]. Such a model has very complex dynamics and contains a variety of transitions down to zero temperature, making it an ideal testing ground for the theory of quantum phase transitions.…”

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confidence: 56%

“…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. The latter are layered superconductors with intrinsic Josephson junctions [5,6,7,8].…”

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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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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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supporting

confidence: 56%

mentioning

confidence: 99%

Spectroscopy of Magnetic Excitations in Magnetic Superconductors Using Vortex Motion

Bulaevskiǐ

Hruška²,

Maley³

2005

Phys. Rev. Lett.

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“…The Josephson nature of the interlayer coupling in this crystal has been confirmed by observation of the double Josephson plasma resonance stemming from two layers in a unit cell [5,6]. According to specific heat measurements [7], magnetic ordering is absent down to a temperature of 0.3 K and a magnetic gap, if any, lies below 0.3 K. They reveal a broad peak near the temperature 1 K and the height of this peak indicates the presence of competing interactions that might be described by the two-dimensional J 1 -J 2 Heisenberg model with J 2 /J 1 > 0.4 [7,14]. Such a model has very complex dynamics and contains a variety of transitions down to zero temperature, making it an ideal testing ground for the theory of quantum phase transitions.…”

Section: Spectroscopy Of Magnetic Excitations In Layered Magnetic Supsupporting

confidence: 53%

“…In Section 2 we consider slightly anisotropic superconductors, i.e., all systems mentioned above except layered superconductors with intrinsic Josephson junctions 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 [5][6][7][8][9]. In this section we introduce the idea of using the electromagnetic coupling of magnetic moments to the ac magnetic field induced by the moving vortex lattice to extract information on the magnetic excitations.…”

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confidence: 99%

Effects of magnetic excitations on the I–V characteristic of magnetic superconductors

Hruška

Boulaevskii

2006

Comptes Rendus. Physique

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Chirality Waves in Two-Dimensional Magnets

2012

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We theoretically show that moderate interaction between electrons confined to move in a plane and localized magnetic moments leads to formation of a noncoplanar magnetic state. The state is similar to the skyrmion crystal recently observed in cubic systems with the Dzyaloshinskii-Moriya interaction; however, it does not require spin-orbit interaction. The non-coplanar magnetism is accompanied by the ground-state electrical and spin currents, generated via the real-space Berry phase mechanism. We examine the stability of the state with respect to lattice discreteness effects and the magnitude of magnetic exchange interaction. The state can be realized in a number of transition metal and magnetic semiconductor systems.Magnetism is a cooperative phenomenon where spins of magnetic ions spontaneously orient relative to each other below certain ordering temperature [1,2]. In principle, arbitrarily complex magnetic orderings are possible; however, the magnetic states encountered in nature tend to be simple, the most common being ferromagnetism (one atom in magnetic unit cell, Fig. 1a) and antiferromagnetism (two distinct atoms in magnetic unit cell, Fig. 1b). More complex orders [3][4][5][6], such as noncollinear spirals ( Fig. 1d) and various noncoplanar orders (e.g., Fig. 1e) are less common, typically arising from the interplay of magnetic exchange interactions, spin-orbit (SO) coupling [5], frustrated lattice structure [3], and magnetic field [6].Noncoplanar magnetism has a unique effect on electronic transport through coherently influencing the quantum-mechanical phase of electrons [7]. The phase accumulates when an electron moves through the magnetic texture and adjusts its spin according to the local magnetic environment. The resulting Berry phase is equal to half of the solid angle subtended by electron spin in the process of its evolution around a closed trajectory (Fig. 1c). This is similar to the Aharonov-Bohm phase induced by the electromagnetic vector potential which couples to electron charge. If the magnetic texture varies significantly on the scale of the material unit cell, the equivalent magnetic field strength can be gigantic, exceeding 10 4 Tesla. Consequently, in non-coplanar magnets one may find such exotic magneto-transport phenomena as the intrinsic anomalous Hall effect [8], Hall effect in the absence of net magnetization or magnetic field [9], or even quantum anomalous Hall effect [10,11].In the absence of SO coupling or magnetic field, the non-coplanar states have been believed to be very rare [12,13]. Recently, however, several examples have been found that show energetic preference for non-coplanar magnetic states [11,[14][15][16][17] in one of the simplest models of magnetism -the isotropic Kondo lattice modeleven in the absence of SO interaction. These noncoplanar states were found for particular lattice structures and electron densities, which leaves an open question: How common are the non-coplanar magnetic states? Here, we show that non-coplanar magnetic states occur in the lowdensity ...

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Magnetic excitations of the 2-D Sm spin layers in

Cited by 3 publications

References 10 publications

Spectroscopy of Magnetic Excitations in Magnetic Superconductors Using Vortex Motion

Spectroscopy of Magnetic Excitations in Magnetic Superconductors Using Vortex Motion

Effects of magnetic excitations on the I–V characteristic of magnetic superconductors

Chirality Waves in Two-Dimensional Magnets

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