Manipulate and control of spin wave and spin flip are crucial for future developments of magnonic and spintronic devices. We present that the spin wave in hexagonal LuMnO 3 single crystal can be selectively excited with laser polarization perpendicular to the c-axis of hexagonal LuMnO 3 and photon energy ~ 1.8 eV. The selective excitation of spin wave also suggests that the spin flip can be selectively controlled in hexagonal manganites. In addition, the physical origin of spin wave correlated with spin flip in hexagonal manganites is discussed.Keywords: spin wave; spin flip; hexagonal manganites; Raman scattering _______________________________________ * Corresponding authors: xchen@wit.edu.cn, yang@ewha.ac.kr 2 Today's electronic devices operate on electron charge. Basing on electron spin, a new generation of smaller, faster, and more efficient spintronic devices could be developed [1][2][3][4][5]. Recently, the idea of magnonic devices, in which spin waves (magnons) are carrying information, has received increasing attention in the magnetics community [6][7][8]. When developing spintronic and magnonic devices, it is crucial to control spin flip and spin wave. Therefore, understand the mechanisms of spin wave and spin flip in magnetic materials, and thus search for convenient method to control spin wave and spin flip would be of great importance for future developments of magnonic and spintronic devices.Hexagonal manganites RMnO 3 (R = rare earth) belong to the class of multiferroic oxides, which possess coexisting magnetic and ferroelectric phases, with crosscorrelation effects between magnetic and electric degrees of freedom [9][10][11][12]. As such, they could potentially be used in applications of electric controlled magnonic and spintronic devices. In this study, we present interesting selective excitation of spin wave in hexagonal LuMnO 3 single crystal, and suggest the mechanism of selective control of spin flip. Also, the physical origin of spin wave correlated with spin flip in hexagonal manganites is discussed.Hexagonal LuMnO 3 single crystal was grown using the traveling floating zone method. The characterizations of magnetization, resistivity, and x-ray powder diffraction have shown super crystalline quality of the single crystal sample. Polarized Raman scattering spectra were obtained in backscattering configuration with a Jobin-Yvon LabRam spectrometer. The single crystal sample was mounted in a helium closed cycle cryostat and the sample temperature was cooled to 20 K.3 Figure 1 shows the Raman scattering spectra of hexagonal LuMnO 3 single crystal obtained at 20 K under three different polarization configuration conditions. The narrow peaks ~ 695 cm -1 and 650 cm -1 can be assigned to A 1 and E 1 phonon mode, respectively.The broad band ~ 815 cm -1 would be originated from spin wave (magnon) scattering [13][14][15]. An interesting feature of Fig. 1 is that the spin wave at ~ 815 cm -1 shows unique polarization selection rule: the spin wave can be excited under z(yx)z configuration, b...

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.intensity ratio of 1655 cm −1 to 1440 cm −1 could be further applied for differentiating different types of PUFAs. With further understanding of relative intensity ratios in various types of UFAs and the development of portable Raman systems, our proposed relative Raman intensity analyses method could be of great interest for practical applications of on-site quality evaluation of edible vegetable oils.

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