CU-NQR STUDY OF SUCCESSIVE MAGNETIC PHASE TRANSITION IN ANTIFERROMAGNETIC YBA2(CU1-XTX)3O6 (T=FE, CO AND NI)

Split spectra of Cu nuclear quadrupole resonance (NQR) in the chain (Cu(1)) site of the antiferromagnetic YBa 2 (Cu 1- x T x ) 3 O 6 (T=Fe, Co, and Ni) show that the spin alignment of Cu moments in the CuO 2 plane changes at a critical concentration of the substitution of Cu by T. The spin structure of the low-temperature magnetic phase is discussed.