63 research outputs found
Magnetic Instability of Pr3Ru4Sn13
We report on the quantum criticality of PrRuSn revealed by our
new material research. PrRuSn has been synthesized by flux
growth and characterized by single X-ray, powder X-ray, and powder neutron
diffraction measurements. The compound adopts a YbRhSn-type
structure with a cubic Pmn. From the magnetization at 1 T, the
effective magnetic moment was estimated to be 3.58 per Pr,
suggesting that the magnetism is mainly contributed by Pr ions. The
specific heat and magnetization show an anomaly at ~ K owing to
the phase transition. The muon spin rotation and relaxation (SR) time
spectra exhibit clear oscillations below . This suggests that the phase is
magnetically ordered. The volume fraction of the magnetic phase estimated from
the initial asymmetry is around ten percent. In addition, spin fluctuations
were observed at low temperatures. These results provide microscopic evidence
that the material is closest to the antiferromagnetically quantum critical
point with a partial order among PrSn ( Co, Ru, Rh).Comment: 14 pages, 4 figures, accepted for publication in J. Phys. Soc. Jp
Coupled spin-charge-phonon fluctuation in the all-in/all-out antiferromagnet Cd2Os2O7
We report on a spin-charge fluctuation in the all-in/all-out pyrochlore magnet Cd2Os2O7, where the spin fluctuation is driven by the conduction of thermally excited electrons/holes and associated fluctuation of Os valence. The fluctuation exhibits an activation energy significantly greater than the spin-charge excitation gap and a peculiar frequency range of 10(6)-10(10) s(-1). These features are attributed to the hopping motion of carriers as small polarons in the insulating phase, where the polaron state is presumably induced by the magnetoelastic coupling via the strong spin-orbit interaction. Such a coupled spin-charge-phonon fluctuation manifests as a part of the metal-insulator transition that is extended over a wide temperature range due to the modest electron correlation comparable with other interactions characteristic for 5d-subshell systems
Na-ion mobility in P2-type Na0.5MgxNi0.17-xMn0.83O2 (0
Sodium transition metal oxides with a layered structure are one of the most widely studied cathode materials for Na+-ion batteries. Since the mobility of Na+ in such cathode materials is a key factor that governs the performance of material, electrochemical and muon spin rotation and relaxation techniques are here used to reveal the Na+-ion mobility in a P2-type Na0.5MgxNi0.17-xMn0.83O2 (x = 0, 0.02, 0.05 and 0.07) cathode material. Combining electrochemical techniques such as galvanostatic cycling, cyclic voltammetry, and the galvanostatic intermittent titration technique with mu+SR, we have successfully extracted both self-diffusion and chemical-diffusion under a potential gradient, which are essential to understand the electrode material from an atomic-scale viewpoint. The results indicate that a small amount of Mg substitution has strong effects on the cycling performance and the Na+ mobility. Amongst the tested cathode systems, it was found that the composition with a Mg content of x = 0.02 resulted in the best cycling stability and highest Na+ mobility based on electrochemical and mu+SR results. The current study clearly shows that for developing a new generation of sustainable energy-storage devices, it is crucial to study and understand both the structure as well as dynamics of ions in the material on an atomic level
Effect of Zn substitution for Cu on CaNaCuOCl near the hole concentration of 1/8 per Cu
A weakening of superconductivity upon substitution of Cu by Zn (0.5~1 %) is
observed in a high-T_c cuprate, Ca_{2-x}Na_xCuO2Cl2, near the hole
concentration of 1/8 per Cu. The superconducting transition temperature and its
volume fraction, estimated by magnetic susceptibility, exhibit a sizable
anomaly for x=0.12~0.14, where the slowing down of Cu spin fluctuations below 5
K is demonstrated by muon spin relaxation experiments. These observations are
in close resemblance to other typical cuprates including YBa2Cu3O_{7-d}, and
Bi2Sr2Ca_{1-x}Y_xCu2O_{8+d}, providing further evidence that Zn-induced
"stripe" correlation is a universal feature of high-T_c cuprate superconductors
common to that of La_{2-x}A_{x}CuO4 (A=Ba, Sr).Comment: 4 pages, 3 figure
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