Eu2+spin dynamics in the filled skutterudites EuM4Sb12(

Abstract

We report evidence for a close relation between the thermal activation of the rattling motion of the filler guest atoms, and inhomogeneous spin dynamics of the Eu 2+ spins. The spin dynamics is probed directly by means of Eu 2+ electron spin resonance (ESR), performed in both X-band (≈ 9.4 GHz) and Q-band (≈ 34 GHz) frequencies in the temperature interval 4.2 T 300 K. A comparative study with ESR measurements on the β-Eu8Ga16Ge30 clathrate compound is presented. Our results point to a correlation between the rattling motion and the spin dynamics which may be relevant for the general understanding of the dynamics of cage systems.

Magnetic polaron effect in Sr8−xEuxGa16GeRosa1, Iwamoto2, Holanda3 et al. 2013Phys. Rev. BSelf Cite10020View full textAdd to dashboardCite

“…From the fit of the resonances to the appropriate admixture of absorption and dispersion, we obtained for x 2.0 an isotropic linewidth H ≈ 310 ± 20 Oe in the X band, which is in agreement with previously reported values for the pure compound Eu 8 Ga 16 Ge 30 . 20,21 However, in the diluted regime (x < 2), there is clearly a narrowing of H , and for the lowest concentration in which we observe ESR resonance (x = 0.04), we obtained a T-independent H ≈ 210 ± 11 Oe. This evident narrowing of the ESR linewidth in the Eu-diluted regime is consistent with the decreasing of Eu 2+ -Eu 2+ spin-interaction contribution to the ESR H .…”

“…Therefore, there are no features indicating a spin-glass-like behavior even though the Einstein temperature, θ E ≈ 60 K, becomes higher than T c . 20 To gain more information about the relaxation mechanism, we performed ESR experiments in the Q band (ν ∼ 34 GHz). Figure 6 displays the temperature dependence of the linewidth in both X and Q bands for x = 6.0.…”

“…In fact, in this case, the measured g shift, g = g experiment − g insulator ≈ 0.005(4), gives, in the simplest scenario of a single-band metal, approximately the measured Korringa rate (i.e., the slope of the H linear increase with increasing temperature), b ≈ 0.8 Oe/K, suggesting a q-independent J fs and the absence of multiband effects. 20,21 On the other hand, it was conjectured that in the Eu 8 Ga 16 Ge 30 compound, a spin-glass-like behavior below θ E may be prevented from occurring by the magnetically ordered state. 20 In this work, we show that for samples where the rattling Einstein temperature θ E lies above the ordering temperature, we still do not observe a broad maximum in the T-dependent ESR linewidth.…”

“…20,21 On the other hand, it was conjectured that in the Eu 8 Ga 16 Ge 30 compound, a spin-glass-like behavior below θ E may be prevented from occurring by the magnetically ordered state. 20 In this work, we show that for samples where the rattling Einstein temperature θ E lies above the ordering temperature, we still do not observe a broad maximum in the T-dependent ESR linewidth. In contrast, the Eu 2+ spin dynamics is dominated by the formation of magnetic polarons.…”

Spin dynamics of S-state ions in the filled skutterudites La1-xRx$Pt4Ge12 (R= Gd, Eu)

“…However, the nature and role of the total vibrational dynamics has been a matter of intense debate in the field, and there are a growing number of experimental [6,7,[11][12][13][14] and theoretical [15][16][17] investigations demonstrating the inadequacy, and exploring possible extensions, of this scenario. Of special interest for the present work are current studies of the spin dynamics in skutterudites, and also in other cage systems, by means of electron spin resonance (ESR) and also nuclear magnetic resonance (NMR) [18][19][20][21][22][23][24][25].…”