Magnetic Interactions between Rare-Earth Ions in Insulators. II. Electron-Paramagnetic-Resonance Measurements of Gd3+ Pair and Gd3+-Eu3+ Interaction Constants in EuCl3

Abstract

Paramagnetic resonance has been observed from both single ions and isolated pairs of ${\mathrm{Gd}}^{3+}$ in Eu${\mathrm{Cl}}_3$ at 77°K and 25.6 GHz. The pair spectra were analyzed in the same way as those observed previously from ${\mathrm{Gd}}^{3+}$ in La${\mathrm{Cl}}_3$. The results give accurate values for the interaction parameters between both nearest (nn) and next-nearest neighbors (nnn). The dominant terms are of the form of isotropic exchange ($J{\mathrm{S}}_1·{\mathrm{S}}_2$), with $J_{\mathrm{nn}}\left(\mathrm{pair}\right)=0.0488\mathrm{}\pm 0.0010$ ${\mathrm{cm}}^{-1\mathrm{}}$ and $J_{\mathrm{nnn}}\left(\mathrm{pair}\right)=-0.0637\mathrm{}\pm 0.0020$ ${\mathrm{cm}}^{-1\mathrm{}}$. The anisotropic parts of the interactions could be accounted for completely by the calculated magnetic dipole-dipole coupling. Combining these results with earlier measurements in La${\mathrm{Cl}}_3$, good estimates can be made of the exchange interactions in pure Gd${\mathrm{Cl}}_3$: $J_{\mathrm{nn}}\left(\mathrm{Gd}{\mathrm{Cl}}_3\right)=0.056\mathrm{}\pm 0.006$ ${\mathrm{cm}}^{-1\mathrm{}}$ and $J_{\mathrm{nnn}}\left(\mathrm{Gd}{\mathrm{Cl}}_3\right)=-0.064\mathrm{}\pm 0.003$ ${\mathrm{cm}}^{-1\mathrm{}}$. These values are in excellent agreement with those inferred from analyses of susceptibility and specific-heat measurements, and they resolve unambiguously earlier uncertainties in the choice of possible parameters. The magnitudes and even the signs of the interactions remain unexplained. From measured $g$-value shifts relative to ${\mathrm{Gd}}^{3+}$ in La${\mathrm{Cl}}_3$ it was also possible to estimate the isotropic part of the ${\mathrm{Gd}}^{3+}$-${\mathrm{Eu}}^{3+}$ exchange interaction: $J_{\mathrm{nn}}(\mathrm{Gd}-\mathrm{Eu})=0.052\mathrm{}\pm 0.030$ ${\mathrm{cm}}^{-1\mathrm{}}$ and

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This publication has 25 references indexed in Scilit:

• Magnetic Interactions between Rare-Earth Ions in Insulators. III. EPR Measurements ofCe3+Pair-Interaction Constants in LaCl3
  Physical Review B, 1968
• Temperature Variation of ${\mathrm{Gd}}^{3+}$ Electron-Spin-Resonance Spectra in La${\mathrm{Cl}}_3$ and La${\mathrm{Br}}_3$ Single Crystals
  Physical Review B, 1967
• Spin-wave calculations for ferromagnetic GdCl₃
  Proceedings of the Physical Society, 1967
• High-temperature expansions for magnetic lattices with arbitrary interactions: Application to GdCl₃
  Proceedings of the Physical Society, 1967
• The magnetic properties of three exchange coupled iridium ions
  Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences, 1965
• Observation of Paramagneticg-Value shifts by Exchange Interactions
  Physical Review Letters, 1963
• Paramagnetic Resonance Absorption in Gadolinium Trichloride
  Proceedings of the Physical Society. Section B, 1957
• Paramagnetic Resonance Absorption in Single Crystals of Diphenylpicrylhydrazyl at Low Temperatures
  The Journal of Chemical Physics, 1955
• Lattice Parameters of Some Rare Earth Compounds and a Set of Crystal Radii
  Journal of the American Chemical Society, 1954
• The Shape of Exchange Narrowed Paramagnetic Resonance Lines
  Physical Review B, 1953

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