Magnetostructural coupling in RFeO (R = Nd, Tb, Eu and Gd).

We investigate the interplay of magnetization and lattice vibrations in rare-earth orthoferrites RFeO, with a specific focus on non-symmetry-breaking anomalies. To do so, we study the magnetization, magnon excitations and lattice dynamics as a function of temperature in NdFeO, TbFeO, EuFeO and GdFeO. The magnetization shows distinct temperature anomalous behavior for all investigated rare-earth orthoferrites, even in the compounds with no phase transitions occurring at those temperatures. Through spin-phonon coupling, these magnetic changes are mirrored by the FeO rotation mode for all the studied RFeO, revealing a common magnetostructural effect associated with the octahedra rotations. The R oscillation modes evidence a Fe/R spins cross-talk for the NdFeO and TbFeO cases. Our work sheds light into the common magnetostructural coupling in rare-earth orthoferrites, and the important role of magnetic anisotropy and spin-orbit coupling strength of the R-Fe interactions on the spin-reorientation transition at high temperatures.