Correlation between magnon and magnetic symmetries of hexagonal RMnO3 (R = Er, Ho, Lu)

Angularly quantized spin rotations in hexagonal LuMnO3

Optical control of the spin degree of freedom is often desired in application of the spin technology. Here we report spin-rotational excitations observed through inelastic light scattering of the hexagonal LuMnO₃ in the antiferromagnetically (AFM) ordered state. We propose a model based on the spin–spin interaction Hamiltonian associated with the spin rotation of the Mn ions, and find that the spin rotations are angularly quantized by 60°, 120°, and 180°. Angular quantization is considered to be a consequence of the symmetry of the triangular lattice of the Mn-ion plane in the hexagonal LuMnO₃. These angularly-quantized spin excitations may be pictured as isolated flat bubbles in the sea of the ground state, which may lead to high-density information storage if applied to spin devices. Optically pumped and detected spin-excitation bubbles would bring about the advanced technology of optical control of the spin degree of freedom in multiferroic materials.

Anomalous Behaviors of Spin Waves Studied by Inelastic Light Scattering

Magnonics, an emerging research field, aims to control and manipulate spin waves in magnetic materials and structures. However, the current understanding of spin waves remains quite limited. This review attempts to provide an overview of the anomalous behaviors of spin waves in various types of magnetic materials observed thus far by inelastic light scattering experiments. The anomalously large asymmetry of anti-Stokes to Stokes intensity ratio, broad linewidth, strong resonance effect, unique polarization selection, and abnormal impurity dependence of spin waves are discussed. In addition, the mechanisms of these anomalous behaviors of spin waves are proposed.

Raman Spectroscopy and 2DCOS Analysis of Unsaturated Fatty Acid in Edible Vegetable Oils

Raman spectroscopy has been applied to study unsaturated fatty acid in edible vegetable oils. The relative intensity ratio of characteristic vibrational bands has been investigated as a function of the content of totally unsaturated fatty acid, polyunsaturated fatty acid, and monounsaturated fatty acid. The results suggest the intensity ratio of 1655 cm−1 to 1440 cm−1 or 1265 cm−1 to 1300 cm−1, i.e., a characteristic vibrational band correlated with carbon-carbon double bond in acid chain to a vibrational band not correlated with double bond, could be applied for preliminary analysis of the content of polyunsaturated fatty acid or monounsaturated fatty acid, but cannot be used to analyze the content of total unsaturated fatty acid. Additionally, two-dimensional correlation spectroscopy (2DCOS) has been performed on the content dependent Raman spectra. The 2DCOS result is consistent with that by Raman spectroscopy.