The saga of YIG: Spectra, thermodynamics, interaction and relaxation of magnons in a complex magnet

Cherepanov, V. B.; Kolokolov, I. V.; L’vov, Victor S.

doi:10.1016/0370-1573(93)90107-o

Cited by 414 publications

(401 citation statements)

References 35 publications

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“…Obviously, the damping parameter in the FePd system is smaller than that in the Fe/W(110) system. The energy dependence of the linewidth in the FePd system is very similar to the one in the materials which are expected to exhibit a low damping, for example, yttrium iron garnet 19 and La 0.7 Ca 0.3 MnO 3 (a representative of magnetic oxides with half-metallic character) 37 . A comparison among different systems is provided in Supplementary Note 4.…”

Section: Resultsmentioning

confidence: 56%

“…If there are no low-energy Stoner excitations, with energies in the range of magnons' energy, the Landau damping will be inoperative and magnons shall live for a longer time. In principle, in ferro(i)magnetic insulators, for example, yttrium iron garnet 19 , or half metals, for example, Heusler alloys 8,9,15 , the low-energy Stoner excitations are not allowed (in insulators, the density of states of both spin-up and spin-down electrons near the Fermi level is zero; and in half metals, the density of states of one spin character near the Fermi level is zero). Therefore, one expects that the Landau damping is not operative and hence terahertz magnons shall exhibit a long lifetime.…”

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confidence: 99%

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Long-living terahertz magnons in ultrathin metallic ferromagnets

et al. 2015

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The main idea behind magnonics is to use the elementary magnetic excitations (magnons) for information transfer and processing. One of the main challenges, hindering the application of ultrafast terahertz magnons in magnonics, has been the short lifetime of these excitations in metallic ferromagnets. Here, we demonstrate that the engineering of the electronic structure of a ferromagnetic metal, by reducing its dimensionality and changing its chemical composition, opens a possibility to strongly suppress the relaxation channels of terahertz magnons and thereby enhance the magnons' lifetime. For the first time, we report on the long-lived terahertz magnons excited in ultrathin metallic alloy films. On the basis of the first-principles calculations, we explain the microscopic nature of the long lifetime being a consequence of the peculiar electronic hybridizations of the species. We further demonstrate a way of tailoring magnon energies (frequencies) by varying the chemical composition of the film.

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Section: Resultsmentioning

confidence: 56%

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confidence: 99%

Long-living terahertz magnons in ultrathin metallic ferromagnets

et al. 2015

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“…Here we use inelastic neutron scattering to study lowenergy ferromagnetic magnons and acoustic phonons in the ferrimagnetic insulator yttrium iron garnet (YIG) with chemical formula [12][13][14]. At zero field and 100 K, we confirm the quadratic wave vector dependence of the magnon energy, E = Dq 2 , where D is the effective spin wave stiffness constant and q is momentum transfer (inÅ −1 or 10 10 m −1 ) away from a Bragg peak [ Fig.…”

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confidence: 79%

“…In the hydrodynamic limit of long wavelength (small-q) and small energies, we expect E = ∆ 0 +gH 0 +Dq 2 for spin wave dispersion, where ∆ 0 is the possible intrinsic spin anisotropy gap, gH 0 is the size of the magnetic field induced spin gap, and D is in units of meVÅ 2 [ Fig. 2(a)] [13][14][15][16]. In addition, for a pure magnetic ordered system without spin-lattice interaction, we expect that χ (Q, E) to be independent of temperature at temperatures well below the magnetic ordering temperature and applied magnetic field after correcting for the field-induced spin gap gH 0 [ Fig.…”

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confidence: 99%

Direct observation of magnon-phonon coupling in yttrium iron garnet

Man

Shi

et al. 2017

Phys. Rev. B

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The magnetic insulator yttrium iron garnet (YIG) with a ferrimagnetic transition temperature of ∼560 K has been widely used in microwave and spintronic devices. Anomalous features in the spin Seeback effect (SSE) voltages have been observed in Pt/YIG and attributed to the magnon-phonon coupling. Here we use inelastic neutron scattering to map out low-energy spin waves and acoustic phonons of YIG at 100 K as a function of increasing magnetic field. By comparing the zero and 9.1 T data, we find that instead of splitting and opening up gaps at the spin wave and acoustic phonon dispersion intersecting points, magnon-phonon coupling in YIG enhances the hybridized scattering intensity. These results are different from expectations of conventional spin-lattice coupling, calling for new paradigms to understand the scattering process of magnon-phonon interactions and the resulting magnon-polarons.Spin waves (magnons) and phonons are propagating disturbance of the ordered magnetic moment and lattice vibrations, respectively. They constitute two fundamental quasiparticles in a solid and can couple together to form a hybrid quasiparticle [1,2]. Since our current understandings of these quasiparticles are based on linearized models that ignore all the high-order terms than quadratic terms and neglect interactions among the quasiparticle themselves [3], magnons and phonons are believed to be stable and unlikely to interact and breakdown for most purposes [4]. Therefore, discovering and understanding how the otherwise stable magnons and phonons can couple and interact with each other to influence the electronic properties of solids are one of the central themes in modern condensed matter physics.In general, spin-lattice (magnon-phonon) coupling can modify magnon in two different ways. First, the static lattice distortion induced by the magnetic order may affect the anisotropy of magnon exchange couplings, as seen in the spin waves of iron pnictides with large inplane magnetic exchange anisotropy [5]. Second, the dynamic lattice vibrations interact with time-dependent spin waves may give rise to significant magnon-phonon coupling [6,7]. One possible consequence of such coupling is to create energy gaps in the magnon dispersion at the nominal intersections of the magnon and phonon modes [8,9], as seen in antiferromagnet (Y,Lu)MnO 3 [10]. Alternatively, magnon-phonon coupling may give rise to spin-wave broadening at the magnon-phonon crossing points [11]. In both cases, we expect the integrated intensity of hybridized excitations at the intersecting points to be the sum of separate magnon and phonon scattering intensity without spin-lattice coupling [8]. Finally, if magnon and phonon lifetime-broadening is smaller than their interaction strength, the resulting mixed quasiparticles can form magnon polarons [6,7].Here we use inelastic neutron scattering to study lowenergy ferromagnetic magnons and acoustic phonons in the ferrimagnetic insulator yttrium iron garnet (YIG) with chemical formula -14]. At zero field and 100 K, we confir...

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“…Up to now, however, most spin transfer torque studies focused on metallic ferromagnets [4][5][6][7][8], while magnetic insulators received much less attention [9][10][11]. However, some magnetic insulators such as yttrium iron garnet (YIG) with extremely low magnetization damping [12] are well suited for the long-range transmission of signals via magnetization dynamics, and may harbor magnon condensates [13] or magnonic crystals [14]. Spin transfer torque and spin pumping [15] provide the communication channel for exploiting insulating magnetic materials in spintronic and electronic devices.…”

Section: Introductionmentioning

confidence: 99%

Current-induced spin torque resonance of a magnetic insulator

et al. 2015

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We report the observation of current-induced spin torque resonance in yttrium iron garnet/platinum bilayers. An alternating charge current at GHz frequencies in the platinum gives rise to dc spin pumping and spin Hall magnetoresistance rectification voltages, induced by the Oersted fields of the ac current and the spin Hall effect-mediated spin transfer torque. In ultrathin yttrium iron garnet films, we observe spin transfer torque actuated magnetization dynamics which are significantly larger than those generated by the ac Oersted field. Spin transfer torques thus efficiently couple charge currents and magnetization dynamics also in magnetic insulators, enabling charge current-based interfacing of magnetic insulators with microwave devices.

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The saga of YIG: Spectra, thermodynamics, interaction and relaxation of magnons in a complex magnet

Cited by 414 publications

References 35 publications

Long-living terahertz magnons in ultrathin metallic ferromagnets

Long-living terahertz magnons in ultrathin metallic ferromagnets

Direct observation of magnon-phonon coupling in yttrium iron garnet

Current-induced spin torque resonance of a magnetic insulator

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