Change in crystal structure and physical properties of the Multiferroics YMnO₃ single crystals by Strong gravitational field

Many researchers have studied the multiferroicity of the hexagonal RMnO₃ (R: rare-earth element) for both applications and fundamental studies. To investigate the relationship between the structure and physical properties of materials, some people apply the chemical pressure effect. The procedure of chemical pressure effect involves substituting rare-earth elements for ones which have a different ionic radius. Mashimo et al. have developed a higherature ultracentrifuge apparatus that can generate extended duration strong gravitational field in excess of 10⁶ G under a wide range of temperatures (up to 500°C). Strong gravitational fields directly act on each atom as a different body force. This can cause the change in crystal structure. Thus, we subjected YMnO₃ single crystal to strong gravity experiments (0.78×10⁶ G, 400°C, 2 h) and investigated the resulting changes in the crystal structure and physical properties of the gravity sample. The single crystal four-circle X-ray diffraction measurements revealed the change in the nearest neighboring Mn-Mn and M-O bond distances. The temperature dependence of magnetic susceptibility by SQUID showed the change in the magnetic anisotropy of gravity sample.