MAGNETIC FIELD INDUCED UNIDIRECTIONAL ANISOTROPY IN ANTIFERROMAGNETS WITH FERROMAGNETIC IMPURITIES L. PÁL, T. TARNÓCZI et G. ZIMMER J. Phys. Colloques, 32 C1 (1971) C1-107-C1-109 DOI: 10.1051/jphyscol:1971133