Sn Mössbauer spectroscopy study of the magnetic properties of the HfFe6Ge6-type compounds: SmMn6Sn4Ge2 and GdMn6Sn4Ge2

The HfFe₆Ge₆-type compound SmMn₆Sn₄Ge₂ has been studied by single-crystal magnetisation and ¹¹⁹Sn Mössbauer spectroscopy. The compound orders ferromagnetically at T_c = 420 K and displays an easy-axis anisotropy from T_c to T_SR = 130 K. Below T_SR, both magnetisation and ¹¹⁹Sn Mössbauer spectroscopy measurements indicate a deviation from the 0 0 1] direction and the presence of easy-cone anisotropy. The angle of the moments with respect to the 0 0 1] direction is estimated to 26-31° from Mössbauer spectroscopy results, in good accordance with the magnetisation results. The isotypic compounds GdMn₆Sn₄Ge₂ and GdMn₆Sn₆ studied by ¹¹⁹Sn Mössbauer spectroscopy display easy plane anisotropy in the whole temperature range 300-4.2 K. The anisotropy behaviours of the LMn₆Sn₄Ge₂ compounds are discussed and the coexistence of easy cone anisotropy for both the SmMn₆Sn₄Ge₂ and HoMn₆Sn₄Ge₂ suggests the play of a positive second-order anisotropy constant of the Mn sublattice.