Y. Nakanishi

De Haas–van Alphen effect in GdAs

Abstract We have for the first time observed de Haas–van Alphen effect in GdAs below the Neel temperature in magnetic fields up to 15xa0T. The Fermi surface consists of three ellipsoidal electron surfaces and a spherical surface. We have also determined the corresponding effective masses and mean free paths. Furthermore, by analyzing the angular dependence of Fermi surface, the number of carriers belonging to each Fermi surface is estimated. It is consistent with that measured by the Hall effect. In Gd X as the lattice constant is increased, the number of carriers decreases. On the other hand, however, GdAs has less carrier concentration compared to that of GdSb.

Magnetization and dHvA effect study of the rare-earth monopnictides in high magnetic fields

Abstract Magnetization measurements of TbSb have been studied in pulsed high magnetic fields up to 30 T. When an external magnetic field H is applied parallel to easy axis [1 1 1], three steps are observed in magnetization process. This suggests complicated magnetic structures in high fields due to electric quadrupole moments. We have also studied dHvA effect of TbSb in high magnetic fields up to 23 T, and observed large spin splittings. From these experimental results, the c-f exchange interaction is estimated to be about 37 meV for H‖ [1 0 0], which means the exchange interaction between carriers and 4f electrons is strong.

MAGNETIC PROPERTIES OF CEXLA1-XSB AND CEXY1-XP IN HIGH MAGNETIC FIELDS

Abstract Magnetic properties of single crystals of Ce X La 1− X Sb and Ce X Y 1− X P have been investigated by magnetization measurements in static or pulsed magnetic fields up to 30xa0T. The magnetic phase diagram was obtained, and the medium state region, FP-phase, is broad compared to the case of CeSb and it appears even at very low temperatures. We have also performed magnetization measurements of Ce 0.95 Y 0.05 P and made a magnetic phase diagram, which is similar to that of CeP. Therefore it is suggested that there are some magnetic layer structures in magnetic fields like in the case of CeP.

Ultrasonic measurements on TmS

Abstract The elastic properties on TmS have been investigated for the first time by means of ultrasonic mesurement. The remarkable softening of the longitudinal ( C 11 − C 12 )/2 mode was observed, while the transverse C 44 mode increases monotonously with decreasing temperature. The bulk modulus C B also shows the anomaly. These behaviors are discussed from the views of the quadrupolar interactions and the unstable 4f state of Tm ion.

Magnetization of Tm monochalcogenides in high magnetic fields

Abstract The magnetization measurements of TmS and TmSe have been performed in pulsed magnetic fields up to 30xa0T. In both the compounds the induced magnetizations along the [1xa00xa00] axis are significantly smaller than those along the other principal axes ([1xa01xa00],xa0[1xa01xa01]) even above T N . The absolute magnetization values of principal axes are reduced compared to the expected values, although the crystal field splitting of 4f levels is negligibly small. They cannot be explained by the crystal field effect only.

The Fermi surface and the magnetization of Ce0.5La0.5Sb

Abstract The measurements of a magnetization and a de Haas–van Alphen effect have been performed first time on the diluted system Ce x La 1− x Sb ( x =0.5). The Fermi surface changes remarkably with decreasing the concentration x . Combining the results obtained by other groups for different concentration, it has been turned out that the spin splitting becomes gradually smaller with increasing concentration of La, i.e. increasing the lattice constant. We have also observed the field dependence of the spin splitting. The Fermi surface is supposed to change depending on x , but even x =0.5 is similar to that of the pure LaSb.

Magnetization and magnetostriction of TmS and TmSe in high magnetic fields

Abstract Magnetization and magnetostriction measurements of single crystals TmS and TmSe have been performed for the first time in high magnetic fields up to 20xa0T to study the anisotropies of these compounds. The magnetization curve of both materials for any axis is almost the same as those for other axes above 50xa0K, which means that anisotropies of these compounds are very small at high temperatures. At low temperature, however, a steep increase of magnetization is observed when an external field is applied to the [1xa00xa00] axis. We have also performed magnetostriction measurement on TmS and it has been turned out that the crystal stretches along the [1xa00xa00] direction in the ordered state for H‖[1 0 0] above transition field. It is considered that the crystalline field parameter O 20 probably plays an important role for the anisotropy observed in the magnetization process of the [1xa00xa00] axis.

Magnetization measurements on CeXLa1−XSb in static and pulsed magnetic fields

Abstract Magnetic properties of single crystals Ce X La 1− X Sb ( X =1, 0.9) have been investigated by magnetization measurements in both static and pulsed magnetic fields. For Ce 0.9 La 0.1 Sb, the magnetization in static fields show two or more steps below 16xa0K. In addition, small steps have been first observed in the FP phase by pulsed field measurements. Therefore, some complicated layer structures like the case of CeSb seem to exist. The transition from the FP phase to ferromagnetic phase in pulsed fields is sharp in the case of static field measurement as well as the case of CeSb, but is broad in the pulsed field measurement, probably due to slow relaxation.

Temperature and field dependence of magnetization on UPd2Al3

Abstract Detailed measurements of magnetization (M) on UPd2Al3 have been made in static magnetic fields up to 27xa0T for H‖a. Below 12xa0K a sharp step, which seems to be a first order transition, has been observed in a M–H curve around H≈18xa0T, and the transition changes to a S-shape anomaly above about 12xa0K. On the other hand, a characteristic feature is observed in M(H,T) even in the paramagnetic phase. We have constructed a magnetic phase diagram, in which there seems to be a “cross-over” region which separates two distinctive magnetic states.

dHvA effect of DySb in quadrupole ordered state

Abstract The dHvA oscillations for DySb is first detected for field direction rotated in the (0 0 1)-(1 1 1)-(1 1 0) plane. The magnetic field was swept from 65–97 kOe, which covered the ferrimagnetic structure with HoP-type and ferromagnetic state. The dHvA signals are quite different between both structures. The conduction-electron Fermi surface located at the Xz point was strongly reduced. It clearly shows that the interaction between the quadrupole moment and the conduction electrons strongly affects the Fermi surfaces for DySb compared to the other RSb.