Abstract-Magnetoelectric spectroscopy of spin excitations in LiCoPO 4

V. Kocsis, S. Bordács, Y. Tokunaga, J. Viirok, L. Peedu, T. Rõõm, U. Nagel, Y. Taguchi, Y. Tokura, and I. Kézsmárki

https://journals.aps.org/prb/abstract/10.1103/PhysRevB.100.155124

We have studied spin excitations in a single-domain crystal of antiferromagnetic ${\mathrm{LiCoPO}}_4$ by terahertz absorption spectroscopy. By analyzing the selection rules and comparing the strengths of the absorption peaks in the different antiferromagnetic domains, we found electromagnons and magnetoelectric (ME) spin resonances in addition to conventional magnetic dipole active spin-wave excitations. Using the sum rule for the ME susceptibility, we determined the contribution of the spin excitations to all the different off-diagonal elements of the static ME susceptibility tensor in zero and finite magnetic fields. We conclude that the ME spin resonances are responsible for the static ME response of the bulk when the magnetic field is along the $x$ axis, and the symmetric part of the ME tensor with zero diagonal elements dominates over the antisymmetric components.

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Abstract-Unidirectional terahertz light absorption in the pyroelectric ferrimagnet CaBaCo4O7

S. Bordács, V. Kocsis, Y. Tokunaga, U. Nagel, T. Rõõm, Y. Takahashi, Y. Taguchi, Y. Tokura

http://arxiv.org/abs/1601.00444

Spin excitations were studied by absorption spectroscopy in CaBaCo4O7 which is a type-I multiferroic compound with the largest magnetic-order induced ferroelectric polarization ({\Delta}P=17mC/m2) reported, so far. We observed two optical magnon branches: a solely electric dipole allowed one and a mixed magnetoelectric resonance. The entangled magnetization and polarization dynamics of the magnetoelectric resonance gives rise to unidirectional light absorption, i.e. that magnon mode absorbs the electromagnetic radiation for one propagation direction but not for the opposite direction. Our systematic study of the magnetic field and temperature dependence of magnon modes provides information about the energies and symmetries of spin excitations, which is required to develop a microscopic spin model of CaBaCo4O7.

Abstract-Unidirectional terahertz light absorption in the pyroelectric ferrimagnet CaBaCo4O7

S. Bordács, V. Kocsis, Y. Tokunaga, U. Nagel, T. Rõõm, Y. Takahashi, Y. Taguchi, and Y. Tokura

Phys. Rev. B 92, 214441 – Published 31 December 2015

https://journals.aps.org/prb/abstract/10.1103/PhysRevB.92.214441

ABSTRACT 

Spin excitations were studied by absorption spectroscopy in CaBaCo4O7 which is a type-I multiferroic compound with the largest magnetic-order induced ferroelectric polarization (ΔP=17 mC/m2) reported, so far. We observed two optical magnon branches: a solely electric dipole allowed one and a mixed magnetoelectric resonance. The entangled magnetization and polarization dynamics of the magnetoelectric resonance gives rise to unidirectional light absorption, i.e., that magnon mode absorbs the electromagnetic radiation for one propagation direction but not for the opposite direction. Our systematic study of the magnetic field and temperature dependence of magnon modes provides information about the energies and symmetries of spin excitations, which is required to develop a microscopic spin model of CaBaCo4O7.

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Abstract-Unidirectional terahertz light absorption in the pyroelectric ferrimagnet CaBaCo4O7

S. Bordács, V. Kocsis, Y. Tokunaga, U. Nagel, T. Rõõm, Y. Takahashi, Y. Taguchi, and Y. Tokura

https://journals.aps.org/prb/accepted/87070Y68Wc51f14ff95a2790416e16664585554e4

Spin excitations were studied by absorption spectroscopy in CaBaCo4O7 which is a type-I multiferroic compound with the largest magnetic-order induced ferroelectric polarization (DP=17 mC/m2) reported, so far. We observed two optical magnon branches: a solely electric dipole allowed one and a mixed magnetoelectric resonance. The entangled magnetization and polarization dynamics of the magnetoelectric resonance gives rise to unidirectional light absorption, i.e. that magnon mode absorbs the electromagnetic radiation for one propagation direction but not for the opposite direction. Our systematic study of the magnetic field and temperature dependence of magnon modes provides information about the energies and symmetries of spin excitations, which is required to develop a microscopic spin model of CaBaCo4O7.