MAGNETO-OPTICAL VISUALIZATION OF CRYSTAL TWINS IN TETRAGONAL ANTIFERROMAGNET Ca3Mn2Ge3O12 V. V. Eremenko, N. F. Kharchenko, S. V. Sofroneev, S. L. Gnatchenko, H. Le Gall et J. M. Desvignes J. Phys. Colloques, 49 C8 (1988) C8-967-C8-968 DOI: 10.1051/jphyscol:19888442