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Cerium hexaboride (CeB6) as a heavy fermion compound displays a number of interesting low-temperature physical properties such as dense Kondo behavior and a complex magnetic phase diagram due to the interaction between itinerant and local electrons. Recently, the electron emission property of CeB6 has received much attention because it has potential applications in replacing the commercial LaB6 cathode and serving as new-generation thermal cathodes. In addition, by comparison with other metal cathodes, it also possesses some advantages, such as a low work function, low volatility, high brightness, thermal stability and high mechanical strength. However, so far the thermionic emission properties of CeB6 single crystal surfaces except for the (100) surfaces have been rarely reported. Whether the different crystal surfaces of CeB6 contribute to the various interesting emission properties is main research purpose of the present work. In this paper, the (110), (111), (210) and (310) crystal surfaces of single crystal CeB6 are determined by the X-ray Laue diffraction method, and their thermionic emission current densities are measured at different temperatures and applied voltages. As a result, the maximum emission current densities of the (110), (111), (210) and (310) crystal surfaces at 1873 K are 38.4, 11.54, 50.4 and 20.8 A/cm2, respectively. When their cathode temperatures are all 1773 K, their maximum emission current densities are 15.2, 5.43, 28.0 and 11.44 A/cm2. In addition, when the cathode temperature decreases to 1673 K, their maximum emission current densities are 4.24, 0.9, 6.2 and 2.43 A/cm2. It means that the thermionic emissions are strongly anisotropic for the different crystal surfaces. In general, the maximum emission current density of (100) crystal surface of LaB6 single crystal is about 10 A/cm2 at 1700 K. By comparing the emission current density of CeB6 single crystal at 1773 K with that of LaB6 at 1700 K, it is found that the emission properties of (210) crystal surface are maybe close to those of LaB6. The work function values of the (110), (111), (210) crystal surfaces calculated by the Richardson-Dushman formula are 2.64, 2.71 and 2.40 eV, respectively. Among these, the (210) crystal surface possesses the smallest value of the work function, which is hopeful for being used as an electron source of scanning electron microscopy. Zero-field magnetoresistivity measurments confirm the transition temperatures of TQ=3.3 K and TN=2.4 K. Field-angle dependent magnetoresistivity measurments show that the electrical resistivity varies between 69 μupΩ·cm and 73 μupΩ·cm when the crystal rotates from the[001] to the[011] direction. This indicates that the electrical resistivity in a magnetic field is also anisotropic.

We present neutron scattering data on $\mathrm{Ce}{({\mathrm{Ru}}_{1\ensuremath{-}x}{\mathrm{Fe}}_{x})}_{2}{\mathrm{Ge}}_{2}$ that show that magnetic ordering in the vicinity of a quantum critical point is restricted to short length scales even though all moments that are present have lined up with their neighbors. We argue that order is not limited by crystallographic defects but rather that quantum fluctuations disorder the system and dilute the magnetic moments to such an extent that a percolation network forms. The latter naturally explains how $E∕T$ scaling is possible in a system whose apparent dimensionality is above the upper critical dimension.

A sample of YBa 2 Cu 3 O 7 was constructed by stacking a number of small single crystals. Magnetization measurements were made in magnetic fields up to 38 T, both parallel to the c -axis and to the basal plane. At 1.4, 4.2 and 20.4 K, a large irreversible magnetization was observed. The significance of these results for the superconducting properties is discussed.

Construction des diagrammes temperature-composition, presentant la region du processus d'aimantation du premier ordre et des diagrammes de phases des spins

Des mesures d'aimantation jusqu'a 35 T a 4,2 K sur Ce 1−x Gd x Al 3 montrent l'existence d'un couplage antiferromagnetique fort dans ce systeme. Pour GdAl 3 , on observe une transition de spin flop vers 6T. Estimation de l'anisotropie et des champs d'echange de GdAl 3

Magnetic isotherms in fields up to 35T have been measured at 4.2 and 77K on magnetically-aligned powders of (Pr,R) 2 Fe 14 B compounds with R = Gd, Nd, Er and Sm. Anisotropy constants up to sixth order have been derived. The influence of the various rare-earth substitutions upon the first-order magnetization process in Pr 2 Fe 14 B has been studied.