Yoshitaka Koi

Line Width of the Pure Quadrupole Resonance of Bromine in NaBrO3

Using a regenerative spectrometer the line widths of the two bromine isotopes in NaBrO 3 were measured at melting ice and liquid oxygen temperatures. The full width at half-maximum intensity of Br 79 is 3.85±0.1 kc and that of Br 81 is 4.09±1 kc. No observable dependence of the line width on temperature was found. From the ratio of the line widths it is concluded that the main cause of the line width in NaBrO 3 is the magnetic dipole interaction, and the contribution from the relaxation is of the order of 0.1 kc.

ESR Study of Hyperfine Coupling Constants of Eu2+ in Alkaline Earth Chalcogenides –Transferred Hyperfine Field in Eu-Chalcogenides

The hyperfine (hf) fields at isolated Eu 2+ ions in alkaline earth chalcogenides are measured by ESR method to make a separation between the core polarization and transferred contributions to the hf field at the Eu nucleus in Eu-chalcogenides. The Eu hf fields, which are assumed to be equal to the core polarization fields in Eu-chalcogenides, are (-)299, (-)300, (-)292 and (-)283 kOe in SrO, SrS, SrSe and SrTe, respectively. Using NMR data, the transferred hf fields at Eu nuclei are estimated as -8, -32, -38 and -30 kOe in the ferromagnetic states of EuO, EuS, EuSe and EuTe, respectively. The variation of the transferred hf field from EuO to EuTe is correlated to the exchange mechanism involving 5d and 6s electron states.

Electron Paramagnetic Resonance Study of Gd3+ and Eu2+ in the Mixed Valence Compound SmB6

The g shifts and linewidths of the Gd 3+ and Eu 2+ EPR in SmB 6 , have been measured in the temperature range between 1.6 and 20 K. The g shifts are independent of temperature and are -0.07 and -0.06 for Gd 3+ and Eu 2+ , respectively, which are attributed to the exchange interaction between the impurity and the 4f electrons of host Sm ions. The effective exchange parameter is estimated to be 1.4 K for Gd 3+ and 1.2 K for Eu 2+ . The linewidth of Gd 3+ increases rapidly with increasing temperature above 4k, while that of Eu 2+ increases rather slowly. The observed difference in the temperature dependences of the linewidths of Gd 3+ and Eu 2+ is discussed in terms of proposed models.

Zeeman Splitting of Nuclear Quadrupole Spectra of NaBrO3

The Zeeman effect of nuclear quadrupole resonance line in a single crystal of sodium bromate is observed in the magnetic field of 3760 gauss. The Zeeman patterns for various crystallographic orientations are investigated and they are compared with the theoretical patterns. From the observed splitting the nuclear magnetic moment of Br 79 is calculated. The value obtained is 2.1033±0.0052 nuclear magnetons.

Nuclear Magnetic Resonance Study of Ferromagnetic β1-MnZn

With the hope of obtaining information about the canted spin structure which has been proposed by Nakagawa et al. on the basis of their neutron diffraction study, the Mn 55 NMR frequency has been measured as a function of external magnetic field. A value of (-1.03±0.03) MHz/kOe has been obtained for d ν/ d H at 77°K. This value seems to suggest that β 1 -MnZn has a simple ferromagnetic spin structure, if it is not the case that the hyperfine field at the Mn 55 nucleus lies accidentally along the ferromagnetic component due to the effects of the neighboring Mn moments. The results of the observation of the Zn 67 NMR is appended. The hyperfine field at the Zn 67 nucleus is -270.9 kOe at 4.2°K.

Temperature Dependence of the Hyperfine Field at Mn55 Nuclei in FCC Cobalt

The hyperfine field at Mn 55 nuclei in fcc cobalt has been measured by means of nuclear magnetic resonance in the range from 4.2 K to 296 K. It decreases much more rapidly than the saturation magnetization with increasing temperature as the hyperfine field at Mn 55 nuclei in iron.