Spin-lattice Interaction For Ions In Low-symmetry Sites: The Case Of Mn2+:caco3

The spin-lattice interaction for Mn2+ ions as substitutional impurities in CaCO3 has been studied by electron-paramagnetic-resonance (EPR) experiments in crystals under externally applied uniaxial stresses. The shifts of the EPR lines of Mn2+ were measured as a function of the stress applied along the three different directions that accept uniaxial forces in this crystal. The values of six second-order spin-lattice coefficients for the Mn2+ site were obtained from the data. We also obtained two conditions relating linear combinations of the other four second-order coefficients. Contributions to the spin-lattice interaction of terms of fourth order in the effective spin have been detected. Our results are used to discuss the effect on the EPR spectrum of the different distortions of the carbonate ions surrounding the Mn2+. © 1994 The American Physical Society.49138583859

Stress Effects On The Esr Spectra Of Rare Earths In Polycrystalline Thin Films

A method for calculating the independent parameters in the spin-lattice Hamiltonian from ESR experiments performed in diamagnetic thin metallic films doped with rare-earth ions is given. One independent parameter is obtained as a function of the orientation of the film when the film is a single crystal. When the film is a polycrystal, one additional parameter is obtained. In the light of the present calculation, the existing data are analyzed as is the validity of previous interpretations. Finally, comments on the future of the technique are presented. © 1986 The American Physical Society.3396491649

Comment On The Gd Crystalline Field And The Gd-pr Exchange In The Van Vleck Monopnictides

We report on the observation of resolved fine structure in the ESR of Gd in PrSb, TmSb, and PrBi single crystals. The fourth-order crystalline-field parameter b4 was found to increase with the lattice constant upon going from the antimonides to the bismuthides, consistent with the variation of b4 in the analogous nonmagnetic pnictides. A correlation between b4 and the Korringa rate in the analogous nonmagnetic compounds suggests that the variation of b4 is associated with conduction-electron effects. Also the variation of the Gd-Pr exchange parameter, JGd-Pr across the pnictides is attributed to variation of the conduction-electron d-d overlap. The data enable us to estimate the pressure derivative of b4 and JGd-Pr. © 1979 The American Physical Society.1942385238

Stress Effects On The Electron-spin-resonance Spectra Of Er In Gold And Silver Thin Films

Electron-spin-resonance measurements were carried out at liquid-helium temperatures on diluted Er in Au and Ag thin films (300-5000) evaporated on NaCl and quartz substrates. The observed anisotropy of the g value, linewidth, and line shape are explained by the mixing of excited crystalline field levels with the 7 ground state: These admixtures are caused by the stresses induced by the difference between the thermal expansion coefficients of the substrate and the film. Lower limits for the tetragonal and trigonal second-order orbit-lattice coupling parameters can be estimated from the data. In Au their magnitude and sign agree with those predicted by the point-charge model, while in Ag the trigonal parameter does not. Qualitative information about the strain distribution across the film was obtained by employing the anisotropy of the g value, the linewidth, and the line shape together with x rays and electron-microscopy analysis. © 1981 The American Physical Society.2373149315

Esr Of Au: Yb Thin Films: Crystal-field Effects And The Kondo Dilemma

ESR experiments at liquid-helium temperatures on Au: Yb thin films evaporated on quartz and NaCl substrates are reported. The anisotropy on the.2294161416

Theory and experiment of the ESR of Co2+^{2+} in Zn2_2 % (OH)PO4_4 and Mg2_2(OH)AsO4_4

Experiments of Electron Spin Resonance (ESR) were performed on Co$$ substituting Zn$^{2+}$ or Mg$^{2+}$ in powder samples of Zn$_2$(OH)PO$_4$ and Mg$_2$(OH)AsO$_4$. The observed resonances are described with a theoretical model that considers the departures from the two perfect structures. It is shown that the resonance in the penta-coordinated complex is allowed, and the crystal fields that would describe the resonance of the Co$^{2+}$ in the two environments are calculated. The small intensity of the resonance in the penta-coordinated complex is explained assuming that this site is much less populated than the octahedral one; this assumption was verified by a molecular calculation of the energies of the two environments, with both Co and Zn as central ions in Zn$_2$(OH)PO$_4$.Comment: 43 pages, LaTex file, 6 figures, EPS. submitted to Journal of Physics Condens

Laser-excited Fluorescence And Electron-spin Resonance Of Er3+ In Polycrystalline Alcl3

The green fluorescence transitions among the levels corresponding to the 4S3/2 and 4I15/2 configurations of Er3+ diluted in AlCl3 have been measured using laser excitation. The data allow us to determine the crystalline-field splittings of these levels and, in turn, the spin-Hamiltonian parameters. The electron-paramagnetic-resonance spectrum observed at low temperatures is in good agreement with that expected from these parameters. © 1990 The American Physical Society.42190991

New Paramagnetic Center In Amorphous Silicon Doped With Rare-earth Elements

A new paramagnetic center associated with rare earths (RE) (La, Ce, Pr, Nd, Gd, Er, and Lu) in amorphous silicon is reported. It is shown that RE impurities are incorporated in a-Si and that the density of paramagnetic dangling bonds decreases as a consequence of the presence of these impurities. An interpretation in terms of RE 6s orbitals and crystal-field-split 5d orbital hybridization suggests that the RE behaves as an acceptor impurity with an associated hole in the a-Si valence-band tail, which is responsible for the observed resonance at a g value of 2.100.01. © 1989 The American Physical Society.3942860286

Electron Spin Resonance Of Nd3+ And Gd3+ In D-band Intermetallic Compounds

We report on the ESR of the rare-earth ions Nd3+, Gd3+, Er3+, and Yb3+ on powdered samples of various intermetallic compounds of AB2 cubic structure where B is a transition-metal ion belonging to the group VIII of the Periodic Table, and A is a nonmagnetic ion (La, Ce, Y). The resonance of the Nd3+ in these compounds originates within a Γ6 crystal-field ground level and exhibits resolved hyperfine satellites for the Nd143 and Nd145 isotopes. The Gd3+ spectra show a single isotropic line. Using our data for Gd3+ and Nd3+ together with results previously published for the AB2 cubic compounds, we were able to show a correlation between the observed g shifts and the position of the B ion in the Periodic Table. This variation is explained qualitatively using a simple multiband model, as well as band-structure arguments. The hyperfine constants for the Nd143 and Nd145 isotopes were found smaller in magnitude with respect to the values in insulators; this effect is attributed to s-electron self-polarization due to the Nd localized-moment-s-electron exchange coupling. The ESR linewidths of LaIr2: Nd and LaRh2: Nd exhibit an exponential thermal dependence at high temperatures which is attributed to the presence of a Γ8 excited level at Δ=90±20 K. © 1979 The American Physical Society.19115495550

Electron Spin Resonance In Amorphous Silicon Doped With Gd

ESR experiments on Gd impurities in amorphous silicon between liquid-He and room temperatures show three resonances which could be ascribed to paramagnetic dangling bonds (g=2.00550.0005), to Gd S7/28 states (g=1.9970.005), and to a new paramagnetic center (g=2.100.05) associated with the presence of Gd atoms. For low-Gd-concentration samples the intensity of the resonance due to dangling bonds decreases as the Gd concentration increases and the intensity of the new paramagnetic center is found to increase with increasing temperature. These results indicate, as we recently found for other rare-earthelement impurities in a-Si, that a fraction of the Gd atoms act as acceptor impurities with associated loosely bound holes in the a-Si valence-band tail which are responsible for the resonance of the new paramagnetic center observed at a g value of 2.100.05. © 1989 The American Physical Society.39128398840