Spin-wave (magnon) scattering, when clearly observed by Raman spectroscopy, can be simple and powerful for studying magnetic phase transitions. In this paper, we present how to observe magnon scattering clearly by Raman spectroscopy, then apply the Raman method to study spin-ordering and spin-reorientation transitions of hexagonal manganite single crystal and thin films and compare directly with the results of magnetization measurements. Our results show that by choosing strong resonance condition and appropriate polarization configuration, magnon scattering can be clearly observed, and the temperature dependence of magnon scattering can be simple and powerful quantity for investigating spin-ordering as well as spin-reorientation transitions. Especially, the Raman method would be very helpful for investigating the weak spin-reorientation transitions by selectively probing the magnons in the Mn 3+ sublattices, while leaving out the strong effects of paramagnetic moments of the rare earth ions.
Bibliographical noteFunding Information:
X.B.C. acknowledges the supports by Wuhan Institute of Technology and National Research Foundation of Korea Grant No. 2010-0022857. I.S.Y. was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIP) (No. 2015001948). The work at Rutgers was supported by the DOE under Grant No. DE-FG02-07ER46382. T.W.N. acknowledges the support by IBS-R009-D1.