G. Ablart

An EPR study of dilute magnetic semiconductors Hg1−xCoxSe (x = 0.0045 and x = 0.0087)

Abstract X-band (≈9.3 GHz) EPR spectra are recorded from room temperature down to 5 K on two samples of symmetry-induced zero band gap semiconductor Hg 1− x Co x Se ( x = 0.0045 and 0.0087), previously subjected to electron bombardment. Both the samples exhibit, in addition to a narrow intense line ( g = 2.018) due to trapped electron/ defect centre, a broad Co 2+ EPR line (overlap of the transitions M s = ± 1 2 ↔ ± 3 2 ) characterized by g = 2.027, which disappears at low temperatures. In addition, only the EPR spectra of the sample with the larger concentration of Co ions reveal the presence of an extra EPR line with the value of g = 2.024 at temperatures below 40 K. (This line was, however, found to be present in another sample with the lower concentration.) This extra line is interpreted to be due to the Kramers doublet (M s = ± 1 2 ) of the Co 2+ ion. The present EPR data do not indicate the presence of Co 3+ ions.

Spin dynamics in the intercalates EuxZrSe1.95

Abstract Electron Spin Resonance (ESR) measurements have been made on powders of the recently prepared intercalates EuxZrSe1.95 in which europium was previously shown to be mostly in its +2 oxidation state. The linewidth evolution against Eu concentration and temperature were obtained using a conventional X-band reflection spectrometer. The spin-lattice relaxation rate, as measured using a modulation spectrometer, is found to contribute importantly to line broadening. The behavior of the studied materials is compared to that of other magnetically diluted Eu2+ systems.

Spin relaxation in TMMC: Evidence of two paramagnetic species

Abstract We have observed in monocrystals of TTMC an anomalous behaviour of the ESR line width, line shape and spin lattice relaxation, when the temperature is varied. These results are explained by the presence of 1 d and 3 d paramagnetic species. The relative concentration of these species has been estimated.

Observation of a spin-lattice relaxation rate dependent on the magnetic field in CuCl2 · 2H2O

Abstract At 77 and 290 K the spin-lattice relaxation rate of cupric chloride was found to present an H 2 magnetic field dependence. The effect could be due to the admixture of excited doublets of the ground multiplet.

Spin-lattice relaxation in glasses doped with Fe2O3

Abstract We investigated the thermal dependence of the electron spin-lattice relaxation time T 1 by the modulation method over the 10 to 290 K temperature range in five silicate or barium vanadate glasses doped with Fe 2 O 3 . Our data are viewed with respect to the theory of Kurtz and Stapleton and are compared to results concerning the optical linewidth.

Field dependence of spin-lattice relaxation in paramagnetic salts

Abstract The field dependence of the Raman SLR rate is determined for H0 of the order of the local field. Both S-state and non S-state transition salts are investigated when (i)Hdip > Hexch and (ii) Hexch > Hdip. Measurements are obtained from the response of the longitudinal magnetization to an amplitude modulated microwave field. The observed dependences agree with Orbach-Huang calculations.

The pair spectrum in diamagnetically doped TMMC

Abstract A symmetrical ten-line structure has been observed in the electron spin-resonance spectrum of quasi one-dimensional (CH3)4NMnCl3(TMMC) doped with diagmagnetic Cd at 20% atomic concentration. This structure, on which is superimposed a single-ion line and a much broader finite chain line, has been attributed to Mn2+ ion pairs. It disappears when the angle φ of the magnetic field with the chain axis exceeds 20°. Because of the rather large linewidth the hyperfine structure was not resolved. The relevant parameters of the fine structure (dipole interaction De and single-ion anisotropy Dc) are somewhat different from those measured in the “symmetrical case” of Mn2+ pairs doped in diamagnetic isomorphous TMCC. In particular it appears that the MnMn distance is smaller in TMMC-Cd. The broadening of lines is related to interactions between paired Mn2+ ions and other Mn2+ ions belonging to neighboring finite chains.