nterplay between magnetic ion and amorphous carbon in Na3V2(PO4)3/C nanocomposite
Cheng-Wei Kao1, Chun-Chuen Yang1*, Chin Wei Wang2, Shu-Han Zhuang3, Yung-Hsiang Tung1, Ting-Wei Hsu1, Wei-Chun Wu1, Wei-Ren Liu3, Kuen-Song Lin4
1Department of Physics, Chung Yuan Christian University, Chung Li, Taoyuan, Taiwan
2Neutron group, National Synchrotron Radiation Research Center, Hsin-Chu, Taiwan
3Department of Chemical Engineering, Chung Yuan Christian University, 200, Chung Pei Rd., Chung Li 32023, Taiwan, Chung Li, Taoyuan, Taiwan
4Department of Chemical Engineering and Material Science, Yuan Ze University, Chung Li, Taoyuan, Taiwan
* Presenter:Chun-Chuen Yang, email:chunchuenyang@cycu.edu.tw
Crystal structure, magnetic and electric properties of Na3V2(PO4)3/C nanocomposite were studied by Neutron and x-ray powder diffraction, Raman spectroscopy, ac magnetic susceptibility, and ac impendence experiments. Na3V2(PO4)3 shows a trigonal structure with R-3c space group while the coated carbon film exhibits amorphous phase as the temperatures are between 5 K and 300 K. The a-axis hold constant while the c-axis increases with temperature. An external magnetic will enlarge the c-axis but no any effect on a-axis. No long-range magnetic ordering existed at the tested temperatures, and a short-range magnetic correlation is found below 220 K. Magnetic-dependence x-ray diffraction experiments refers that the one mT magnetic field is equivalent to 1.4(2) K thermal effect on the c-axis. The carbon film exhibits Raman peaks of D1-, D3-, D4-, and G-bands. The D1-band shows red-shift as a magnetic field exist which is originated from the nature of the diamagnetic behavior of the carbon ions. The G-band peak also displays the red-shift as warming above 220 K under an applying magnetic field, which is associated with the spin-phonon interaction. Ac magnetic susceptibility curve follows the Curie-Weiss law. The magnetic moment of V3+ and Curie temperature TC of the sample are 2.91(6) μB/f.u. and the 15(4) K, respectively. Ac impedance experiments show Z value increased with decreasing excitation frequencies and approaches to 5.3×103 Ω-cm as f=0 Hz. The external magnetic field shows no any effect on Z at 300 K. This study represents a possibility of the lattice and phonon control via applying an external magnetic field. It may be useful in the lithium or sodium ion batteries.

Keywords: Na3V2(PO4)3, nanocomposite, Raman spectrum, spin-phonon