Antiferromagnetic resonances in twinned EuFe2As2 single crystals

In this paper, we report the results of magnetic resonance spectroscopy of ${\mathrm{EuFe}}_{2}{\mathrm{As}}_{2}$ single crystals. We observe magnetic resonance responses, which are attributed to antiferromagnetic resonances of the Eu sublattice with orthorhombic crystal structure and with different orientations of twin domains relative to the external field. We confirm the validity of the recently proposed spin Hamiltonian with anisotropic Eu-Eu exchange interaction and biquadratic Eu-Fe exchange interaction.