A. Tsujimura

Nuclear magnetic resonance study of RCo5 = Y, Ce, Pr, Nd, Sm, Gd, Tb, Dy and Ho

Abstract The nuclear magnetic resonance of 59 Co nuclei in magnetic domains of RCo 5 (R = Y, Ce, Pr, Sm, Gd, Tb, Dy and Ho) has been measured under external fields up to about 55 kOe at 4.2 K. To assign the observed NMR signals to each Co site, the 59 Co nuclear magnetic resonance of R(Co 1− x ) 5 has also been measured under the same conditions. The results of NMR studies show that the orbital contribution to the 59 Co hyperfine field is very large at the 2c site in RCo 5 .

The coexistence of ferromagnetic and antiferromagnetic interactions in the GdMn12 compound

Abstract The coexistence of ferro- and antiferromagnetic interactions are investigated for the GdMn 12 compound where the interaction between the Gd atoms is weakly ferromagnetic due to the separation by the antiferromagnetic coupling Mn-Mn pair. The magnetic interactions in the case of T c ⪡ T N are also discussed for TbMn 12 and HoMn 12 .

Magnetic properties of Y(Co1−xTx)2-hydrides (T = Ni, Al)

Magnetization measurements have been performed on the hydrides Y(Co1−xTx)2Hy (T = Ni, Al) at 4.2 K. In all hydrides, ferromagnetism has been observed. The occurrence of ferromagnetism in the hydrides may be ascribed to a lattice expansion ( = 7%) by hydrogen absorption and an electron transfer.

1H NMR study of YT2-hydride (T = Fe, Mn)

Abstract In the hydrides YMn 2 H 3.0 , the nuclear magnetic resonance of 1 H nuclei has been measured under external fields up to 50 kOe at 4.2 K and three 1 H NMR signals have been observed. The 1 H hyperfine fields corresponding to these NMR signals can be discussed in terms of the dipole interaction between the H nuclei and the localized moments of the Mn(or Fe) atoms surrounding H atoms.

Spin reorientations in (Nd1-xYx)2Co14B compounds

Abstract Magnetization measurements and 59 Co NMR have been performed for (Nd 1− x R x ) 2 Co 14 B(R=Y, Pr, Sm, Gd and Tb) compounds. Three types of the spin phase diagrams, depending on the sign of the Stevens factor of the R ion, have been established based on these measurements. The results are discussed with the crystalline electric field (CEF) approximation.

Magnetic properties of Sm2(Co1−xTx)14B (T = Mn, Fe, Ni)

The 59 Co NMR and magnetic measurements in Sm 2 (Co 1− x T x ) 14 B (T = Mn, Fe, Ni) have been carried out at 4.2 and 77 K, respectively. The 59 Co hyperfine fields in Sm 2 (Co 1− x T x ) 14 B increase for T = Fe, and decrease for T = Mn, Ni with increasing T-concentration. These results show that the 59 Co hyperfine fields depend on nearest neighbor T atoms.

The anomalous behaviour of Gd atoms (Fe1−xMnx)2 compounds

Abstract The educed Gd atoms in the X-structure (Th 6 Mn 23 -type) of Gd(Fe 1− x Mn x ) 2 were magnetically investigated by comparing with Gd 6 (Fe 1− y Mn y ) 23 whose structure is Th 6 Mn 23 -type. The magnetic properties of Gd(Fe 1− x Mn x ) 2 (0.4≤ x ≤0.7) were observed to be quite similar to those of Gd 6 (Fe 1− y Mn y ) 23 (0.4≤ y ≤0.7).

NMR study of R(Fe1-xCox)3-hydride

Abstract The NMR signals of 59Co in R(Fe1-xCox)3Hy (R = Y, Gd) were measured by the spin echo method at 77 K. The results show that the hyperfine fields at 59Co nuclei of CoI and CoIII sites decrease and the hyperfine field at 59Co nuclei of CoII site increases upon hydrogen absorption.

Hyperfine fields at 89Y nuclei in Y(Fe1−xTx)3 (T= Al, Co)

Abstract The spin echo spectra of 89 Y hyperfine fields in Y(Fe 1− x T x ) 3 with low concentration x consist of two main lines and of satellite lines caused by the replacement of the Fe atoms by the T atoms. Values of the magnetic moments of the T atoms are estimated by observing the satellite lines.

NMR study of Laves phase (Mg1−xRx)Co2 compounds

Abstract Nuclear magnetic resonances of 59 Co nuclei in (Mg 1− x R x )Co 2 (R = Y, Gd) compounds at 4.2 K have been observed for 0⩽ x ⩽1. By replacing Mg with R, the 59 Co hyperfine field decreases or is nearly constant in the C14 range and increases in the C15 range. These results are explained by the difference of the contribution from R atoms.