View article

dc magnetization, ac magnetic susceptibility, and microwave magnetoabsorption measurements on rare-earth cuprates, R 2 CuO 4 (R= Tb, Dy, Ho, Er, Tm, and Y), synthesized under high pressure, indicate the presence of antiferromagnetic order with a weak-ferromagnetic component below a characteristic temperature T 0. From the maximum in the amplitude of the microwave absorption, we have determined T 0= 295 (3) K for R= Tb. The values of T 0 decrease monotonically along the series down to T 0= 260 (3) K for R= Tm. For R= Y we have measured T 0= 265 (3). The in-phase component of the ac magnetic susceptibility χ’(T) presents a peak whose shape and intensity are dependent on both the amplitude and the frequency of excitation of the magnetic field. The simultaneous observation of a nonzero and also frequency-dependent out-of-phase term, χ’’(T), suggests the presence of relaxation phenomena …