Spontaneous magnetization in the diluted low-anisotropy antiferromagnets K₂FeCl₅.H₂O:In

Abstract

Spontaneous magnetization and monodomain behaviour were observed, at zero applied field, in single crystals of the diluted low-anisotropy antiferromagnets K2Fe1-xInxCl5.H2O. The spontaneous magnetization M appears at the Neel temperature, and is directed along the easy axis (either up or down). The magnitude of M depends on x. For x=0.15 and 4,2 K, M corresponds to 0.2% of the calculated saturation magnetization. The spontaneous moment appears only when substitution is made at the Fe site, replacing K by Rb, or Cl by Br, does not lead to a spontaneous moment. This is the first observation of a spontaneous moment in any diluted low- anisotropy antiferromagnet.