nterplay between magnetic ion and amorphous carbon in Na3V2(PO4)3/C nanocomposite

Cheng-Wei Kao¹, Chun-Chuen Yang^1*, 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