Effects of the interplay between R 4f and Fe 3d on magneto-electric behavior and high field magnetization in RFe2O4 (R = Yb, Tm)

Abstract The detailed magnetization behavior of RFe2O4 (R = Yb and Tm) have been investigated in a wide range of magnetic fields. In low temperature region, the temperature dependence of magnetization shows that the strength of the interaction between R 4f and Fe 3d ions is directly related to the R3+ ions, a distinct phase transition was observed at ~53 K in YbFe2O4 and no obvious one was observed in TmFe2O4 even cooling to 1.8 K. The possible interaction between R 4f and Fe 3d ions and their evolution with magnetic field were investigated by pulsed high magnetic field. Based on the structures of both FeO5 trigonal bipyramid and RO6 octahedron of RFe2O4, the competition between ferromagnetic double-exchange and antiferromagnetic superexchange among the R-R, R-Fe and Fe-Fe, especially the interplay between R and Fe ions, are discussed. The different R-Fe magnetic interaction betweenYbFe2O4 and TmFe2O4 is experimentally verified by impedance spectroscopy and dielectric spectroscopy. Finally, the high field magnetic phase diagrams of RFe2O4 (R = Yb, Tm) are proposed.