High-temperature electromagnons in the magnetically induced multiferroic cupric oxide driven by intersublattice exchange.
Magnetically induced ferroelectric multiferroics present an exciting new paradigm in the design of multifunctional materials, by intimately coupling magnetic and polar order. Magnetoelectricity creates a novel quasiparticle excitation--the electromagnon--at terahertz frequencies, with spectral signatures that unveil important spin interactions. To date, electromagnons have been discovered at low temperature (<70 K) and predominantly in rare-earth compounds such as RMnO3. Here we demonstrate using terahertz time-domain spectroscopy that intersublattice exchange in the improper multiferroic cupric oxide (CuO) creates electromagnons at substantially elevated temperatures (213-230 K). Dynamic magnetoelectric coupling can therefore be achieved in materials, such as CuO, that exhibit minimal static cross-coupling. The electromagnon strength and energy track the static polarization, highlighting the importance of the underlying cycloidal spin structure. Polarized neutron scattering and terahertz spectroscopy identify a magnon in the antiferromagnetic ground state, with a temperature dependence that suggests a significant role for biquadratic exchange.
Department of Physics, Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, UK.
S P P
SP
Jones
Department of Physics, Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, UK.
S M
SM
Gaw
Department of Physics, Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, UK.
K I
KI
Doig
Department of Physics, Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, UK.
D
D
Prabhakaran
Institut Laue-Langevin, BP156, F-38042 Grenoble, France.
E M
EM
Hétroy Wheeler
Department of Physics, Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, UK.
A T
AT
Boothroyd
1] Department of Physics, Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, UK [2] Department of Physics, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK.
J
J
Lloyd-Hughes
D003300:Copper / Q000737:chemistry*; D058085:Iron Compounds / Q000737:chemistry*; D008280:Magnetics / Q000295:instrumentation* / Q000379:methods*; D013696:Temperature
D058085:Iron Compounds; D003300:Copper; C030973:cupric oxide