Spin reorientation transitions in DyFeO3induced by magnetic fields

Mossbauer spectrometry was used to study spin reorientation transitions in single crystals samples of DyFeO 3 . In agreement with magnetisation data of Belov (1974), a Morin transition was observed at 35+or-3K where the coupled Fe 3+ ions reorient from a magnetic structure having an antiferromagnetic vector parallel to the crystal a axis and weak ferromagnetism along the crystal c axis ( Gamma 4 ) to a pure antiferromagnetic structure along the crystal b axis ( Gamma 1 ). Spin reorientations were induced with an external field. At 270, 130 and 77K fields applied parallel to the a axis caused continuous rotation of the Fe 3+ antiferromagnetic vector from the a to the c axis ( Gamma 4 to Gamma 2 ) the rotation being complete as fields of 7.5, 6.7 and 5.5 T respectively. At 4.2K a field parallel to the b axis induced a transition Gamma 1 to Gamma 4 at a critical field H cr =0.75+or-0.1 T. Reorientations were also observed at 4.2K in which the antiferromagnetic vector rotated in a plane perpendicular to the applied field: a field parallel to the c axis caused a rotation of the antiferromagnetic axis from b to a ( Gamma 1 to Gamma 4 with H cr =0.7+or-0.1 T) and a field parallel to the a axis caused the antiferromagnetic axis to rotate from b to c ( Gamma 1 to Gamma 2 with H cr =1.6+or-0.4 T). A model incorporating Dy 3+ -Fe 3+ interactions is discussed to explain the reorientations.