Role of the rare earth in lattice and magnetic coupling in multiferroic h−HoMnO3

J Liu (1) , Y Gallais (1) , M-A Méasson (1) , A Sacuto (1) , S W Cheong , M Cazayous (1)

1 MPQ (UMR_7162) - Laboratoire Matériaux et Phénomènes Quantiques

We used Raman scattering to study the lattice and magnetic excitations in the hexagonal HoMnO 3 single crystals. The E 2 phonon mode at 237 cm −1 is affected by the magnetic order. This mode is related to the displacement of Mn and O ions in the a-b plane and modulates the Mn-O-Mn bond angles in the a-b plane and in the in-plane Mn-Mn superexchange interaction. The mode at 269 cm −1 associated to the displacement of the apical Ho 3+ ions along the c direction presents an abrupt change of slope at T N , showing that the role of the rare-earth ions cannot be neglected in the magnetic transition. We have identified magnon and crystal-field excitations. The temperature dependence of the magnetic excitations has been compared to the Mn and Ho moment and indicates that the exchange-interaction pattern between Mn and Ho atoms drives the uniaxial anisotropy gap above the Mn-spin-rotation transition.

Domaines: Electrons fortement corrélés [cond-mat.str-el]

J Liu, Y Gallais, M-A Méasson, A Sacuto, S W Cheong, et al.. Role of the rare earth in lattice and magnetic coupling in multiferroic h−HoMnO3. Physical Review B, 2017, 95, ⟨10.1103/physrevb.95.195104⟩. ⟨hal-03003749⟩