Effect of Cr and Mn ions on the structure and magnetic properties of GaFeO₃: role of the substitution site

Abstract

Effect of substitution of Cr and Mn in the Fe and Ga sites of GaFeO₃ on the structural parameters and magnetic properties has been investigated by preparing GaFe_1-xCr_x(Mn_x)O₃ and Ga_1-xCr_x(Mn_x)FeO₃ starting with appropriate oxide precursors. It is shown that, starting with Cr or Mn substituted Ga₂O₃, one obtains Ga_1-xCr_x(Mn_x)FeO₃, while reaction of Cr or Mn substituted α-Fe₂O₃ with Ga₂O₃ yields GaFe_1-xCr_x(Mn_x)O₃. The structural parameters and magnetic properties vary significantly with the substitution site of Cr showing a large decrease in the unit cell parameters as well as the T_C and other magnetic properties when the substitution is at the octahedral Fe (1, 2) site. Substitution of Cr at the octahedral Ga2 site results in marginal changes. Substitution of Mn in the Ga and Fe sites also show differences although the changes themselves are much smaller. First-principles calculations confirm such site-specificity and show how Cr substitution affects the properties differently when substituted at the Ga2 and Fe1 sites.