Ferromagnetic feature from Mn near room temperature in the fine particles of GdMn₂Ge₂ and TbMn₂Ge₂

Abstract

The magnetization behaviors of GdMn₂Ge₂ and TbMn₂Ge₂ in the bulk and in the fine particles (< 1 μm) obtained by high-energy ball-milling are compared. Pronounced modifications in the spontaneous, remanent and high-field magnetization in the fine-particle form, attributable to Mn, are observed. The results indicate that the antiferromagnetism of Mn sublattice known for the bulk form in the range ~100-300 K gets weakened in favor of ferromagnetism in the fine particles. On the basis of this observation, we infer that there are other factors like size (and possibly defects) also play a role to decide the exact nature of magnetic ordering of Mn in this ternary family of materials, in contrast to the traditionally held view that the basal plane Mn-Mn distance is the crucial controlling parameter.