A Way to Create Mn-Containing GdFe3(BO3)4 and the Dopant Effecton Its Magnetic Properties

A wide series of substitutions in a subsystem of small radii cations M = Al, Cr, Fe, Ga, Sc is possible in rare-earth borates ReM3(BO3)4 with the huntite structure. However, the existence of these compounds where M = Mn still raises doubts. The study presents a synthetic approach developed in the framework of the flux method allowing for the required conditions for introducing Mn into the huntite structure and growing single crystals from the GdFe3-хMnx(BO3)4 solid solution. Special attention is paid to the choice of the solvent and elaboration of intermediate chemical bonds formed between the components of the solvent and crystal-forming part during synthesis. Isometric dark-brown crystals of GdFe3-хMnx(BO3)4 slightly elongated along the c axis, with x = 0.27 and the size up to 5×4×4 mm3, were obtained, with the X-ray powder analysis confirming the structure to be identical to that of pure GdFe3(BO3)4. Notably, their lattice parameters were larger despite the equivalence of the ionic radii of Fe3+ and Mn3+ cations. The analysis of the thermal and field magnetization dependences of the synthesized GdFe3-хMnx(BO3)4 revealed a series of low-temperature features in the form of a shift of the temperatures TN and TSF as compared to those characteristic for unsubstituted GdFe3(BO3)4 and a new feature was observed to be added at TС = 16 K to a cascade of phase transitions due to the presence of manganese in the structure.