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⁵¹V-NMR experiments have been performed to investigate the local magnetic and electronic properties of the mixed-valence oxide δ-Ag_2/3V₂O₅, which shows the novel V⁴⁺/V⁵⁺ charge ordering trigged by Ag ion ordering. We have observed the abrupt loss of ⁵¹V-NMR signal coming from the non-magnetic V⁵⁺-like ions above T_c = 225 K. It indicates that the majority of V ions are magnetic above T_c and that the phase transition is accompanied by the charge separation and the charge ordering of 3d electrons on V sites. In the low-temperature phase below T_c, the nuclear spin-lattice relaxation rate 1/T₁ shows the thermal activation-type temperature dependence with the activation energy of about 130 K. It has been clarified that the ground state of this material is the charge ordered one with the spin singlet of 3d electrons on V⁴⁺-V⁴⁺ pair from a microscopic point of view.

We carried out ¹³⁹La-, ²⁹Si- and ¹⁹⁵Pt-NMR measurements of LaPt₂Si₂ which shows coexistence of a superconducting state and a charge density wave (CDW) state. Slight gradual decreasing ∼0.006% are observed in Knight shifts of ¹³⁹La and ²⁹Si-line C from 200K to 5K. The decreasing are much less than the previous ¹⁹⁵Pt-NMR spectra PeakD's shifts reported in T. Kubo et al, so the decreasing can be expected following ¹⁹⁵Pt-Knight shift decreasing. LaPt₂Si₂ has two types of Pt-sites: Pt(1)2a(Wycoff position) and Pt(2)2c. By carrying out single crystalline ¹⁹⁵Pt-NMR, the site assignments of ¹⁹⁵Pt-NMR spectra to each respective Pt sites are succeeded for both H||a and ||c. Associating for 1/T₁T results for polycrystalline powder reported by T. Kubo et al, Pt(1)-site may contributes to the CDW order below T*. It is necessary to measure the temperature dependences of line1's 1/T₁T by using single crystalline LaPt₂Si₂.