Magnetic transition and spin rotation in a new multiferroic Ba3TaFe3Si2O14 observed by the Mossbauer spectroscopy

The long-range 3D magnetic ordering in the Fe3+-containing langasite family compound Ba3TaFe3Si2O14 was observed below 27K with the iron lattice split into two nonequivalent magnetic sublattices. The appearance of the nonequivalent Fe sites is associated with the structural phase transition P321 -> P3 induced by the magnetic ordering. At this transition, the presence of the polar threefold axis creates the conditions for the ferroelectric state and Ba3TaFe3Si2O14 may be considered as a magnetically induced multiferroic. The Fe3+ magnetic moments in the two sublattices are oriented at different angles to the local crystal axes with a mean value similar to 45 degrees. At temperatures between 4.2 and 25 K, iron spins in two sublattices rotate in opposite directions which can be related to the magnetic chirality in the helicoidal magnetic structure. Copyright (c) EPLA, 2010