Observation of an inter-sublattice exchange magnon in CoCr${}_2$O${}_4$ and analysis of magnetic ordering

Abstract

We report on an investigation of optical properties of multiferroic CoCr${}_2$O${}_4$ at terahertz frequencies in magnetic fields up to 30 T. Below the ferrimagnetic transition (94 K), the terahertz response of CoCr${}_2$O${}_4$ is dominated by a magnon mode, which shows a steep magnetic-field dependence. We ascribe this mode to an exchange resonance between two magnetic sublattices with different $g$-factors. In the framework of a simple two-sublattice model (the sublattices are formed by Co${}^{2+}$ and Cr${}^{3+}$ ions), we find the inter-sublattice coupling constant, $\lambda =-(18\pm 1)$ K, and trace the magnetization for each sublattice as a function of field. We show that the Curie temperature of the Cr${}^{3+}$ sublattice, ${\Theta }_2$ = $(49\pm 2)$ K, coincides with the temperature range, where anomalies of the dielectric and magnetic properties of CoCr${}_2$O${}_4$ have been reported in literature.

arXiv commentaccepted to PRB

References in corpus (5)

• Possible evidence for electromagnons in multiferroic manganites
• Electromagnons in multiferroic YMn2O5 and TbMn2O5
• Dielectric anomalies and spiral magnetic order in CoCr2O4
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Cited by in corpus (4)

• Spin-Hall magnetoresistance and spin Seebeck effect in spin-spiral and paramagnetic phases of multiferroic CoCr2O4 films
• Magnetic properties of strained multiferroic CoCr2O4: a soft X-ray study
• Magnons and Magnetodielectric Effects in CoCr${}_2$O${}_4$: Raman Scattering Studies
• Emergent magnetic state in (111)-oriented quasi-two-dimensional spinel oxides