EVIDENCE OF PRESSURE-INDUCED ANTIFERROMAGNETISM IN FERROMAGNETIC HO0.4GD0.6

The rare earth alloy Ho0.4Gd0.6 was examined under uniaxial pressure a pplied along the c axis by means of magnetic susceptibility vs tempera ture. At ambient pressure the compound happened to be ferromagnetic at all temperatures where magnetic ordering occurs. Nevertheless, at pre ssures larger than p=700 bars there is clear evidence of an antiferro magnetic phase (likely to be helical one) that occurs just below the m agnetic ordering temperature. This result is consistent with the hypot hesis that the cia ratio is the crucial parameter for the occurrence o f helical structure in heavy rare-earth metals.