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The Hill plot is a well-known criterion of the f-electron element interatomic threshold distance separating the nonmagnetic state from the magnetic state in actinides and lanthanides. We have reinvestigated the Hill plot of Ce compounds using the commercial crystallographic database CRYSTMET, focusing on a relationship between the Ce-Ce distance and the magnetic ordering temperature because a Ce compound with no other magnetic elements rarely has a magnetic ordering temperature that is higher than 20 K. The Hill plot of approximately 730 compounds has revealed that a Ce compound, particularly a ferromagnet, showing a high magnetic ordering temperature would require a short Ce-Ce distance with a suppression of the valence instability of the Ce ion. From the study, we developed interest in Ce2AuP3 with a Curie temperature of 31 K. The ferromagnetic nature of this material has been examined in terms of a doping effect, which suggests a possible increase in magnetic anisotropy energy. [ABSTRACT FROM AUTHOR]

The Hill plot is a well-known criterion of the f-electron element interatomic threshold distance separating the nonmagnetic state from the magnetic state in actinides and lanthanides. We have reinvestigated the Hill plot of Ce compounds using the commercial crystallographic database CRYSTMET, focusing on a relationship between the Ce-Ce distance and the magnetic ordering temperature because a Ce compound with no other magnetic elements rarely has a magnetic ordering temperature that is higher than 20 K. The Hill plot of approximately 730 compounds has revealed that a Ce compound, particularly a ferromagnet, showing a high magnetic ordering temperature would require a short Ce-Ce distance with a suppression of the valence instability of the Ce ion. From the study, we developed interest in Ce2AuP3 with a Curie temperature of 31 K. The ferromagnetic nature of this material has been examined in terms of a doping effect, which suggests a possible increase in magnetic anisotropy energy. [ABSTRACT FROM AUTHOR]

The microstructure, phase reaction characteristics and mechanical properties of fabricated Al–20%Mg 2 Si in situ composite with different contents of cerium have been investigated using optical microscopy, scanning electron microscopy, X-ray diffraction, thermal analysis and hardness tests. The results show that addition of Ce not only refined Mg 2 Si reinforcement particles but also changed the morphology of eutectic Al–Mg 2 Si, Al 5 FeSi (β) intermetallic and Al 5 Cu 2 Mg 8 Si 6 (Q) + Al 2 Cu (Ɵ) phases. It was found that 0.8 wt% Ce is the optimum concentration to transform the phases into refined structures. The structure of the skeleton of Mg 2 Si P changed to a polygonal shape with uniform distribution and decrease in size from 124 μm to 60 μm and increased in density from 12 to 45 particles/mm 2 . Flake-like Mg 2 Si E transformed into a rod-like morphology. In addition, the aspect ratio of needle-like β structures reduced from 40.5 to 22.9, accompanied with an increase of solid fraction for Q + Ɵ phase. Ce addition increased the nucleation temperature of Mg 2 Si P and β phases; however, it had an opposite effect for the Mg 2 Si E and Q + Ɵ phases. The composite hardness increased from 61.32 to 74.15 HV because of refinement of the microstructure. The refining mechanism of Mg 2 Si P and Mg 2 Si E phases is discussed in the current study, and formation of new Ce compounds is believed to be responsible for the refinement effect. [ABSTRACT FROM AUTHOR]

The Laves phase compound CePt 2 crystallizing in the cubic C15 (MgCu 2 type) structure orders antiferromagnetically at 1.8 K. Single crystalline samples of Ce 1− x Pb x Pt 2 (0 < x < 0 . 5) have been prepared by the self-flux method. It is found that Pb atoms replace preferentially the Ce atoms in the face-center-cubic sublattice, forming a superlattice structure of the cubic C15b (MgSnCu 4 type). We have measured the specific heat, magnetic susceptibility, and electrical resistivity. The results reveal that the Ce valence remains trivalent in Ce 1− x Pb x Pt 2 ( x ⩽ 0.43) but the superlattice formation suppresses the antiferromagnetic ordering temperature below 0.35 K for x = 0.43. [ABSTRACT FROM AUTHOR]

Crystal growth, luminescence, and scintillation properties of a CeBr3 crystal are presented. The crystal was grown with Bridgman method using two-zone transparent furnace and cut to ϕ10 × 10 mm³. The investigation of luminescence and scintillation properties of the CeBr3 was performed under the excitation by ultraviolet and γ-rays at room temperature. The emission spectrum of the CeBr3 was observed in the range of near ultraviolet to violet, which is due to 5d → 4f transition of the Ce3+. The decay time of the Ce3+ emission was measured to be approximately 20 ns. The energy resolution of the CeBr3 single crystal was obtained to be 4.9% for the 137Cs 662 keV γ-ray. The relative signal of the CeBr3 crystal by the 137Cs γ-ray is about three times higher than that of a CsI:Tl crystal when bi-alkali PMT was used. The nonproportionality in the γ-ray energy of the crystal was also measured. The study showed that the CeBr3 crystal is the promising candidate for the PET application. The CeBr3 crystal with high light output and fast decay time affords its use for the particle detection in high counting rate environment such as nuclear and high-energy physics. [ABSTRACT FROM AUTHOR]

Abstract: Temperature and field-dependent magnetization measurements on polycrystalline CeMnCuSi2 reveal that the Mn moments in this compound exhibit ordering with a ferromagnetic (FM) component ordered instead of the previously reported purely antiferromagnetic (AFM) ordering. The FM ordering temperature, T c, is about 120K and almost unchanged with external fields up to 50kOe. Furthermore, an AFM component (such as in a canted spin structure) is observed to be present in this phase, and its orientation is modified rapidly by the external magnetic field. The Ce L 3-edge X-ray absorption result shows that the Ce ions in this compound are nearly trivalent, very similar to that in the heavy fermion system CeCu2Si2. Large thermomagnetic irreversibility is observed between the zero-field-cooled (ZFC) and field-cooled (FC) M(T) curves below T c indicating strong magnetocrystalline anisotropy in the ordered phase. At 5K, a metamagnetic-type transition is observed to occur at a critical field of about 8kOe, and this critical field decreases with increasing temperature. The FM ordering of the Mn moments in CeMnCuSi2 is consistent with the value of the intralayer Mn–Mn distance R a Mn–Mn=2.890Å, which is greater than the critical value 2.865Å for FM ordering. Finally, a magnetic phase diagram is constructed for CeMnCuSi2. [Copyright &y& Elsevier]

A new type of abrasive particle for polishing the dielectric layer on silicon wafers has been synthesized by modifying colloidal silica with cerium ions. Cerium ions in active silicic acid were titrated into a basic solution at 100 °C to modify the surface of the colloidal silica. The new abrasive particles are easily suspended in an aqueous medium. The removal rate of the dielectric film was higher when the modified colloidal silica was used for polishing than when the original colloidal silica was used as a polishing slurry. The effects of cerium-ion concentration [Ce4+] and seed concentration on the mean particle size of modified colloidal silica and the polishing performance of colloidal silica were investigated in the present study. [Copyright &y& Elsevier]

Abstract: We report on results of X-ray powder diffraction, magnetization and specific heat measurements of the pseudo-ternary (Ce1− x La x )PdIn2 system with x=0; 0.2; 0.4 and 0.6. The results show a linear increase of the unit cell volume and a reduction of the ferromagnetic transition as La content increases. The Debye temperature, Sommerfeld coefficient and crystal field parameters were estimated from specific heat data, and are found to be weakly dependent of the Ce concentration. Also, the variation of magnetic entropy at T C is only weakly dependent on x (ΔS≅0.92Rln2) indicating that T K/T C is approximately constant along the series. The T C and T K behaviors are explained by the variation of the exchange parameter due to the volume change when Ce is replaced by La. Our results indicate that the chemical pressure is the dominant effect rather than the chemical disorder for determining the physical proprieties of the (Ce1− x La x )PdIn2 system. [Copyright &y& Elsevier]

The crystal structure of the CeIr3 compound was refined for the first time from single-crystal X-ray diffraction data, down to R=0.0490, wR2=0.1052. This compound crystallizes in the PuNi3 structure type, space group R&3macr;m (a=5.290(2) Å, c=26.220(4) Å, Z=9, V=635.44 Å3, ρ=16.835 g cm-3, μ=156.36 mm-1). CeIr3 belongs to the R2m+nM4m+5n family, where m and n are the numbers of MgCu2- and CaCu5-type slabs, respectively. For CeIr3, m and n were found to be both equal to 1. [Copyright &y& Elsevier]