Magnetic behaviour of TbCu4Ag and DyCu4Ag

The temperature dependences of DC and AC magnetisation, electrical resistiv ity and magnetoresistivity of TbCu4Ag and DyCu4Ag are reported. In contrast to previous studies which indicate TbCu4Ag to be a simple antiferromagnet and DyCu4Ag to be a ferromagnet, our study indicates a more complicated beh aviour for these materials. We observe three magnetic transitions for TbCu4 Ag, viz. at T-C = 20K, T-1 = 11K and T-2 = 2.5 K. At temperatures T less th an or equal to 10 K the magnetic isotherms show metamagnetic behaviour, whi le for T-1 less than or equal to T less than or equal to T-C our results su ggest canted antiferromagnetism For DyCu4Ag magnetic transitions an observe d at T-C = 19 K and in the vicinity of 5 K. Also for this material there is evidence suggesting a canted antiferromagnetic spin structure. (C) 2000 El sevier Science B.V. All rights reserved.