Papers by Keyword: Paramagnetism

Abstract: We have presented the results of detailed studies of oxygen vacancy and niobium (Nb) substituted spinel Li4Ti5O12 (LTO) materials using first-principles method within the framework of the density functional theory (DFT). We have shown that the ground state of oxygen vacancy and Nb substituted LTO is paramagnetic (PM), and the Nb substitution is most stable on the 16d sites of both the Li and Ti ions. We have indicated that the Nb substitution in the 16d site of Li ion become the n-type metallic material. But the oxygen vacancy containing NbT i substituted LTO is changed from the p-type to the n-type, as increased a concentration of Nb ions.

Abstract: The coexistence of ferromagnetism and paramagnetism of T’-Pr_2-xCe_xCuO_4+α-δ (T’-PCCO) nanoparticles with x = 0, and 0.10 have been studied intensively in the normal state. All samples were synthesized by a chemically dissolved method using HNO₃ as a dissolving agent. The calcination process was performed at 1000°C for 15 h in air and followed by reduction annealing at 700°C in argon atmosphere for 10 h. All samples were first characterized by an x-ray diffraction (XRD) measureemnts followed by Rietveld and Maximum Entropy Method (MEM) analyseis. The result confirms the Ce-dependence and reduction annealing effect on the electron density at around the Cu site. The magnetic characterization was performed by using vibration sample magnetometer (VSM) indicating weak ferromagnetic properties at x = 0 and dominant paramagnetic properties at x = 0.10 at room temperature. Moreover, the weak ferromagnetic feature seems to remain after the annealing process. This signifies the coexist of weak ferromagnetism and paramagnetism at the normal state due to a number of oxygen vacancies in the crystal structure.

Abstract: A novel ternary compound, namely U₃Pt₁₂Si_4, which is best described by the crystallographic formula U₃Pt_12+x-ySi_4-x-z (x = 0.15, y = 0.23, z = 0.16), has been discovered in the U-Pt-Si phase diagram. It crystallizes in a hexagonal unit cell (P6₃/mmc space group) with a = 8.7267(1) Å and c = 9.3385(2) Å. Its structure is an ordered variant of the EuMg_5.2 type with partial occupancies of the Si 4e and Pt 2b positions and mixed Si/Pt occupancy of the 6g site. Magnetic properties measurements revealed that the compound is a Curie-Weiss paramagnet with an effective magnetic moment μ_eff = 3.18 μ_B. Its low temperature specific heat is moderately enhanced (its Sommerfeld coefficient γ is equal to 79(1) mJ mol_U^-1 K^-2) and the electrical resistivity exhibits some characteristic features of dense Kondo lattices.

Abstract: A fitting procedure of the Curie-Weiss law, eliminating the temperature independent contribution (0) from the experimental susceptibility data, was used for determination of the magnetic parameters, i.e. a Curie constant, a Curie-Weiss temperature and an effective magnetic moment, because the theoretical considerations showed that the Curie-Weiss law is invalid for 0  0, even small. This method revealed for the HgCo(NCS)4 paramagnet, commonly accepted as a magnetic susceptibility standard, 0 = 2.43710-6 cm3/g, while for the ZnCr2Se4 antiferromagnet, known as a matrix of various diluted systems, – 0 = -2.56610-6 cm3/g, for comparison.

Abstract: We have studied the magnetic susceptibility, magnetization and electron paramagnetic resonance (EPR) in the diluted magnetic semiconductor Pb1-x-yMgxYbyTe. The magnetic susceptibility of this system is a superposition of the matrix diamagnetism, the paramagnetic contribution of electrons localized in the ytterbium band, and the Curie-Weiss paramagnetism provided by Yb3+ ions. The concentration of Yb3+ ions monotonically increases with the ytterbium content, while a significant fraction of ytterbium ions remains in a nonmagnetic Yb2+ state. A pronounced hyperfine structure was revealed in the EPR spectra. It was ascribed to the interaction between the electron magnetic moment of an unfilled electron shell of Yb3+ ions and nuclear magnetic moment of the 173Yb isotope. The estimated values of the effective g-factor (g1.997 0.002) and the hyperfine-interaction constant (173A=0,56 cm-1) were found to be almost independent of both alloy composition and temperature.

Abstract: The structural and magnetic properties as well as the electron paramagnetic resonance in Pb1-xVxTe (х0.7 at.%) solid solutions have been investigated. It was found that the magnetic field and the temperature dependences of magnetization have a paramagnetic character, connected obviously with the paramagnetic contribution of vanadium impurity isolated ions. Electron paramagnetic resonance spectra were measured and the temperature dependence of the g-factor in the temperature range 85-200 K was obtained.