REMANENT MAGNETIZATION IN THE LINEAR-CHAIN ANTIFERROMAGNET (CH3NH3)MN(1-X)M(X)CL3-CENTER-DOT-2H(2)O, M=CD OR CU

The substitution of small amounts of Mn2+ by Cu2+ or Cd2+ ions in the linear chain antiferromagnet (CH3NH3)MnCl3 . 2H(2)O (T-N=4.12 K) leads to the appearance of a remanent magnetic moment in the substituted co mpound. Magnetization measurements carried out in single crystals reve aled that the remanent magnetization (M(r)) appears along the directio n of the easy axis when the sample is cooled through the ordering temp erature in the presence of an axial magnetic field as low as few milli oersteds. Samples with x similar to 0.01 of Cu and x=0.008 of Cd were investigated. The measured magnetization M=M(r)+H-chi parallel to(axia l) observed at applied axial fields H-axial=0.8 Oe in both crystals is almost entirely due to the contribution of M(r) since H-chi parallel to(axial) is very small. Hysteresis curves were also obtained for the Cd diluted system and the results shows that at T=1.5 K a reversal in the direction of M(r) is obtained for H-axial around 200 Oe. A compari sion with previous recent observations in some three-dimensional dilut ed antiferromagnets is made. (C) 1996 American Institute of Physics.