Narrowing effects in the ESR spectra of Gd in metals: Application to LaSb:Gd

Abstract

The ESR spectra of Gd in metallic single crystals of LaSb exhibit appreciable variation in the ESR line shape upon changing the temperature from 1.7 to 300 K. At low temperatures, a completely resolved fine-structure splitting appropriate to Gd in a cubic crystalline field is observed. The fourth-order cubic-crystalline-field parameter is b4 --+ 32+ 2 Oe. The increase of the temperature leads to significant narrowing effects with the result of a single anisotropic line at room temperature. A Korringa relaxation rate of AH K/T = 0,19 + 0.03 Oe/K was extracted from the thermal broadening of the collaosed spectrum. The thermal broadening of the -1/2~+1/2 fine-structure transition is considerably enhanced, however, with respect to this Korringa thermal broadening. All these features are in complete agreement with the predictions of the theory for exchange narrowing of the fine structure in metals. The ESR line shape was calculated using this theory. Comparison of the theoretical line shape with the one observed experimentally indicates the presence of an additional narrowing mechanism, This narrowing is due to Gd spin-spin interaction in LaSb. The line shape analysis yields an exchange-interaction parameter of 0.03 eV between the spin of Gd and that of the conduction electron. The same value for the exchange parameter is derived, independently, from the experimental Korringa thermal broadening.

Crystal-field study in rare-earth-doped semiconducting YBiPt

“…But we showed above that the A 4 and A 6 CFP obtained for the non-S-state ions, Er 3ϩ , Nd 3ϩ , and Yb 3ϩ in YBiPt are of the same order of magnitude as those reported for rare earths in other cubic materials, where CFE were observed in the ESR spectra of Gd 3ϩ . [18][19][20][21] It suggests that CFE should be present in the ESR of Gd 3ϩ -doped YBiPt, specially when considering the relative small Gd 3ϩ ESR residual linewidth (Ϸ40 Oe͒. Thus the absence of CFE in the ESR spectrum of Gd 3ϩ in YBiPt is yet not understood.…”

Thermally activated exchange narrowing of the Gd3+ESR fine structure in a single crystal of Ce1−xGdGarcia1, Venegas2, Pagliuso3 et al. 2011Phys. Rev. B

“…Figure 7 shows the angular dependence of ∆H at different T corresponding to Regions II and III. Following the analysis of Urban et al 29 for the exchange narrowing of the Gd 3+ ESR fine structure, the anisotropy of ∆H in Region II can be fitted to the general expression for the intermediate coupling regime:…”

Exchange and crystal field effects in the ESR spectra ofEu2+inLaB6

“…Our experiments are performed at concentrations where the conduction electron static susceptibility is much smaller than that of the local moments. In that limit the susceptibility for a system in the unbottleneck regime 39,45,47 is given by…”

“…where p is the angular dependence in a cubic environment 47 and the brackets are the matrix elements of the fourth order CF operator.…”