Structure and Unusual Magnetic Properties of Mg-Containing Solid Solutions Based on Y2FeTaO7.

Mg-containing solid solutions based on Y₂FeTaO₇ and formed by various mechanisms of heterovalent substitution were synthesized and had the following compositions: Y₂Fe_0.55Mg_0.3Ta_1.15O₇, Y₂Fe_0.625Mg_0.3Ta_1.075O₇, Y₂Fe_0.7Mg_0.3TaO₇, Y₂Fe_0.7Mg_0.2Ta_1.1O₇, Y₂Fe_0.85Mg_0.15TaO₇, Y_1.85Mg_0.15Fe_0.925Ta_1.075O₇, and Y_1.85Mg_0.15FeTaO₇. It was shown that all synthesized solid solutions have a pyrochlore-like layered structure (space group P3₁21), in which Fe³⁺ ions are distributed over three structural positions. The magnetic properties of these solid solutions are due to the presence of a small ferromagnetic component in a predominantly antiferromagnetic system and characterize a ferrimagnet or a canted antiferromagnet with the Néel transition at the Néel temperature T_N above room temperature. According to the data of magnetic measurements, two magnetic phase transitions to the ordered phase occur in all the studied samples. Along with the T_N transition, in weak magnetic fields and below T_N, there is a second transition, which is most likely due to a spin reorientation of the Morin type. The existence of magnetic ordering at room temperature in one magnetic sublattice or an internal magnetic field (H_in) was confirmed by Mössbauer spectroscopy. [ABSTRACT FROM AUTHOR]