Microwave absorption in the frustrated ferrimagnet Cu2OSeO3

Kobets, M. I.; Dergachev, K. G.; Khatsko, E. N.; Rykova, A. I.; Lemmens, P.; Wulferding, Dirk; Berger, H.

doi:10.1063/1.3319505

Cited by 19 publications

(23 citation statements)

References 7 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In zero field the lowest energy excitation is a parabolically dispersing Goldstone mode associated with the reduction of symmetry from SU(2) to U(1) in the ferrimagnetic state 29,[42][43][44] . Application of magnetic field gaps the Goldstone mode, which is hereafter referred to as the uniform mode, by an amount proportional to the field through Zeeman coupling 36,64 . Figure 7 displays the results of our high field transmission experiments in which the uniform mode is observed.…”

Section: Thz Dynamics Of the Uniform Modementioning

confidence: 99%

Low-energy magnon dynamics and magneto-optics of the skyrmionic Mott insulator Cu2OSeO3

et al. 2017

View full text Add to dashboard Cite

In this work, we present a comprehensive study of the low energy optical magnetic response of the skyrmionic Mott insulator Cu2OSeO3 via high resolution time-domain THz spectroscopy. In zero field, a new magnetic excitation (f0 = 2.03 THz) which has not been predicted by spin-wave theory is observed and shown, with accompanying time-of-flight neutron scattering experiments, to be a zone folded magnon from the R to Γ points of the Brillouin zone. Highly sensitive polarimetry experiments performed in weak magnetic fields, µ0H < 200 mT, observe Faraday and Kerr rotations which are proportional to the sample magnetization, allowing for optical detection of the skyrmion phase and construction of a magnetic phase diagram. From these measurements, we extract a critical exponent of β = 0.35 ± 0.04, in good agreement with the expected value for the 3D Heisenberg universality class of β = 0.367. In large magnetic fields, µ0H > 5 T, we observe the magnetically active uniform mode of the ferrimagnetic field polarized phase whose dynamics as a function of field and temperature are studied. In addition to extracting a g eff = 2.08 ± 0.03, we observe the uniform mode to decay through a non-Gilbert damping mechanism and to possesses a finite spontaneous decay rate, Γ0 ≈ 25 GHz, in the zero temperature limit. Our observations are attributed to Dzyaloshinkii-Moriya interactions, which have been proposed to be exceptionally strong in Cu2OSeO3 and are expected to impact the low energy magnetic response of such chiral magnets.

show abstract

Section: Thz Dynamics Of the Uniform Modementioning

confidence: 99%

Low-energy magnon dynamics and magneto-optics of the skyrmionic Mott insulator Cu2OSeO3

et al. 2017

View full text Add to dashboard Cite

show abstract

“…[32][33][34][35][36][37][38][39][40][41][42] This system crystallizes in the noncentrosymmetric space group P 2 1 piezoelectricity and piezomagnetism but not for a spontaneous polarization. The structure is a three-dimensional (3D) array of distorted corner-sharing tetrahedra of copper spin S = 1/2 ions.…”

Section: 1629-31mentioning

confidence: 99%

Magnetoelectric effects in single crystals of the cubic ferrimagnetic helimagnet Cu2OSeO3

et al. 2012

Self Cite

View full text Add to dashboard Cite

We present magnetodielectric measurements in single crystals of the cubic spin-1/2 compound Cu2OSeO3. A magnetic field-induced electric polarization (P) and a finite magnetocapacitance (MC) is observed at the onset of the magnetically ordered state (Tc = 59 K). Both P and MC are explored in considerable detail as a function of temperature (T), applied field Ha, and relative field orientations with respect to the crystallographic axes. The magnetodielectric data show a number of anomalies which signal magnetic phase transitions, and allow to map out the phase diagram of the system in the Ha-T plane. Below the 3up-1down collinear ferrimagnetic phase, we find two additional magnetic phases. We demonstrate that these are related to the field-driven evolution of a long-period helical phase, which is stabilized by the chiral Dzyalozinskii-Moriya term D M·(∇×M) that is present in this non-centrosymmetric compound. We also present a phenomenological LandauGinzburg theory for the MEH effect, which is in excellent agreement with experimental data, and shows three novel features: (i) the polarization P has a uniform as well as a long-wavelength spatial component that is given by the pitch of the magnetic helices, (ii) the uniform component of P points along the vector (, and (iii) its strength is proportional to η 2 − η 2 ⊥ /2, where η is the longitudinal and η ⊥ is the transverse (and spiraling) component of the magnetic ordering. Hence, the field dependence of P provides a clear signature of the evolution of a conical helix under a magnetic field. A similar phenomenological theory is discussed for the MC.

show abstract

“…These Cu 4 "molecules," with an effective spin of S = 1, are the elementary magnetic building blocks of Cu 2 OSeO 3 instead of the single Cu ions. The effective spins of the Cu 4 tetrahedra are ferromagnetically coupled and form a trillium lattice, just as the Mn and Fe ions do in the B20 structure of the metallic skyrmion compounds MnSi and FeGe.Prior to the undertaking of the present work, previous studies of the magnetic excitation spectra of Cu 2 OSeO 3 were conducted using Raman scattering [16] and microwave resonance absorption [17], i.e., techniques that are sensitive only to excitations in the center of the Brillouin zone. In contrast, inelastic neutron scattering (INS) is able to measure at finite momentum transfer and is therefore uniquely suited to probe the magnetic excitation spectra of Cu 2 OSeO 3 throughout reciprocal space.…”

mentioning

confidence: 99%

“…Prior to the undertaking of the present work, previous studies of the magnetic excitation spectra of Cu 2 OSeO 3 were conducted using Raman scattering [16] and microwave resonance absorption [17], i.e., techniques that are sensitive only to excitations in the center of the Brillouin zone. In contrast, inelastic neutron scattering (INS) is able to measure at finite momentum transfer and is therefore uniquely suited to probe the magnetic excitation spectra of Cu 2 OSeO 3 throughout reciprocal space.…”

mentioning

confidence: 99%

“…We find that no set of parameters can coax the hitherto applied model to reproduce these two features seen in our data. Due to the fact that zone-center measurements show the dispersion at to have a gap no larger than ∼12 μeV [17], any single-ion anisotropy is likely to be small and we expect instead that these unexplained features are related to the network of antisymmetric, i.e., Dzyaloshinskii-Moriya (DM), interactions in this material [25]. These chiral interactions are ultimately responsible for the stabilization of the slightly incommensurate helical ground state and field-induced skyrmion phases [8,12,26].…”

mentioning

confidence: 99%

See 1 more Smart Citation

Spin excitations in the skyrmion hostCu2OSeO3

et al. 2016

View full text Add to dashboard Cite

We have used inelastic neutron scattering to measure the magnetic excitation spectrum along the high-symmetry directions of the first Brillouin zone of the magnetic skyrmion hosting compound Cu 2 OSeO 3 . The majority of our scattering data are consistent with the expectations of a recently proposed model for the magnetic excitations in Cu 2 OSeO 3 , and we report best-fit parameters for the dominant exchange interactions. Important differences exist, however, between our experimental findings and the model expectations. These include the identification of two energy scales that likely arise due to neglected anisotropic interactions. This feature of our work suggests that anisotropy should be considered in future theoretical work aimed at the full microscopic understanding of the emergence of the skyrmion state in this material. [8], and in the polar magnetic semiconductor GaV 4 S 8 [9]. To understand the formation and the microscopic origin of these skyrmion phases, one needs a multiscale approach that covers the macroscopic domain of the skyrmion as well as the quantum scale of the local spins. This, however, breaks down in the above-mentioned metals because the low-energy delocalized electrons and magnetic degrees of freedom are mixed, intrinsically involving multiple energy and spatial scales.Among cubic helimagnets, Cu 2 OSeO 3 is the only insulator with magnetoelectric properties in the ground state [8,[10][11][12][13][14]. It offers an ideal laboratory to explore the microscopic ingredients that lead to skyrmion formation in a quantitative manner, since its Bloch-type ground-state properties and low-energy excitations are fully governed by the magnetic interactions between localized spins and are not affected by the presence of itinerant carriers. Exchange pathway considerations, susceptibility measurements, and ab initio calculations reveal that two magnetic energy scales divide the system into weakly coupled Cu 4 tetrahedra [15]. These Cu 4 "molecules," with an effective spin of S = 1, are the elementary magnetic building blocks of Cu 2 OSeO 3 instead of the single Cu ions. The effective spins of the Cu 4 tetrahedra are ferromagnetically coupled and form a trillium lattice, just as the Mn and Fe ions do in the B20 structure of the metallic skyrmion compounds MnSi and FeGe.Prior to the undertaking of the present work, previous studies of the magnetic excitation spectra of Cu 2 OSeO 3 were conducted using Raman scattering [16] and microwave resonance absorption [17], i.e., techniques that are sensitive only to excitations in the center of the Brillouin zone. In contrast, inelastic neutron scattering (INS) is able to measure at finite momentum transfer and is therefore uniquely suited to probe the magnetic excitation spectra of Cu 2 OSeO 3 throughout reciprocal space. The additional information afforded by INS therefore provides more rigorous tests of theoretical models aimed at describing the excitation spectra of Cu 2 OSeO 3 .Single crystals of Cu 2 OSeO 3 (cubic P 2 1 3 space group, a = 8.82Å) were gro...

show abstract

Microwave absorption in the frustrated ferrimagnet Cu2OSeO3

Cited by 19 publications

References 7 publications

Low-energy magnon dynamics and magneto-optics of the skyrmionic Mott insulator Cu2OSeO3

Low-energy magnon dynamics and magneto-optics of the skyrmionic Mott insulator Cu2OSeO3

Magnetoelectric effects in single crystals of the cubic ferrimagnetic helimagnet Cu2OSeO3

Spin excitations in the skyrmion hostCu2OSeO3

Contact Info

Product

Resources

About