Magnetic transitions in CaMn7O12 : a Raman observation of spin-phonon couplings

Abstract

The quadruple Calcium manganite (CaMn7O12) is a multiferroic material that exhibits a giant magnetically-induced ferroelectric polarization which makes it very interesting for magnetoelectric applications. Here, we report the Raman spectroscopy study on this compound of both the phonon modes and the low energy excitations from 4 K to room temperature. A detailed study of the Raman active phonon excitations shows that three phonon modes evidence a spin-phonon coupling at TN2 = 50 K. In particular, we show that the mode at 432 cm-1 associated to Mn(B)O6 (B position of the perovskite) rotations around the [111] cubic diagonal is impacted by the magnetic transition at 50 K and its coupling to the new modulation of the Mn spin in the (a,b) plane. At low energies, two large low energy excitations are observed at 25 and 47 cm-1. The first one disappears at 50 K and the second one at 90 K. We have associated these excitations to electro-magneto-active modes.

References in corpus (9)

• Role of the Dzyaloshinskii-Moriya interaction in multiferroic perovskites
• Giant improper ferroelectricity in the ferroaxial magnet CaMn7O12
• Multiferroic Properties of CaMn${}_7$O${}_{12}$
• Giant Ferroelectric Polarization of CaMn7O12 Induced by a Combined Effect of Dzyaloshinskii-Moriya Interaction and Exchange Striction
• Modulated spin helicity stabilized by incommensurate orbital density waves in a quadruple perovskite manganite
• Possible coupling between magnons and phonons in multiferroic CaMn7O12
• Soft vibrational mode associated with incommensurate orbital order in multiferroic CaMn${}_7$O${}_{12}$
• Improper magnetic ferroelectricity of nearly pure electronic nature in cycloidal spiral CaMn${}_7$O${}_{12}$
• Soft phonon driven orbital order in CaMn7O12

Cited by in corpus (1)

• Signatures of magnetostriction and spin-phonon coupling in magnetoelectric hexagonal 15R-BaMnO3