Acta Phys. -Chim. Sin. ›› 2008, Vol. 24 ›› Issue (12): 2153-2158.doi: 10.1016/S1872-1508(08)60081-9

• ARTICLE • Previous Articles     Next Articles

Dynamical Spin Chirality and Magnetoelectric Effect of α-Glycine

SHEN Xin-Chun, WANG Wen-Qing, GONG Yan, ZHANG Yan   

  1. Beijing National Laboratory for Molecular Sciences, Department of Applied Chemistry, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, P. R. China; School of Medicine, Tsinghua University, Beijing 100084, P. R. China; School of Physics, Peking University, Beijing 100871, P. R. China
  • Received:2008-07-07 Revised:2008-09-30 Published:2008-12-04
  • Contact: WANG Wen-Qing

Abstract: Dynamical spin chirality of α-glycine crystal at 301-302 K was investigated by DC (direct current)-magnetic susceptibility measurement at temperatures ranging from2 to 315 Kunder the external magnetic fields (H=±1 T) parallel to the b axis. The α-glycine crystallizes in space group P21/n with four molecules in a cell, which has centrosymmetric charge distribution. The bifurcated hydrogen bonds N+(3)—H(8)…O(1) and N+(3)—H(8)…O(2) are stacked along the b axis with different bond intensities and angles, which formanti-parallel double layers. Atomic force spectroscopy result at 303 K indicated that the surface molecular structures of α-glycine formed a regular flexuous framework in the b axis direction. The strong temperature dependence is related to the reorientation of NH+3 group and the electron spin flip-flop of (N+H) mode. Under the opposite external magnetic field of 1 T and -1 T, the electron spins of N+(3)—H(8)…O(1) and N+(3)—H(8)…O(2) flip-flop at 301-302 K. These results suggested a mechanism of the magnetoelectric effect based on the dynamical spin chirality of (N +H), which induced the electric polarization to produce the onset of pyroelectricity of α-glycine around 304 K.

Key words: α-Glycine, Dynamical spin chirality, Magnetoelectric effect, Pyroelectricity, DC-magnetic susceptibility, Atomic force spectroscopy