Raman scattering studies of the magnetic ordering in hexagonal HoMnO3 thin films

• Published in: Journal of Raman spectroscopy 2010-09, Vol.41 (9), p.983-988
• Main Authors: Minh Hien, Nguyen Thi, Chen, Xiang-Bai, Hoang, Luc Huy, Lee, D., Jang, S.-Y., Noh, T. W., Yang, In-Sang
• Format: Article
• Language: English
• Subjects: Aluminum oxide; HoMnO3; Laser ablation; Magnetic transitions; magnon; Neel temperature; Order disorder; phonon-magnon coupling; Raman scattering; Raman spectra; Spin exchange; Thin films
• ISSN: 0377-0486; 1097-4555; 1097-4555
• DOI: 10.1002/jrs.2531

We present the results of the temperature dependence of the Raman spectra of hexagonal HoMnO3 thin films in the 13–300 K temperature range. The films were grown on Pt(111)//Al2O3 (0001) substrates using the laser ablation method. In the HoMnO3 thin films, we initially observedseveral broad Raman peaks at ∼510, 760, 955, 1120, and 1410 cm−1. These broad Raman peaks display an anomalous behavior near the magnetic transition temperature, and the intensity difference of the Raman spectra at different temperatures shows several pairs of negative and positive peaks as the temperature is lowered below the Néel temperature. Our analyses indicate that all the broad peaks are correlated with magnetic ordering, and we have assigned the origin of all the broad peaks. Purely on the basis of the Raman analysis, we have deduced the Néel temperature and the spin exchange integrals of HoMnO3 thin films. We also investigated the effects of the growth condition on the strongest broad peak at ∼760 cm−1, which is related with pure magnetic ordering. This result indicates that the oxygen defect in the HoMnO3 sample has negligible effect on magnetic ordering. Copyright © 2009 John Wiley & Sons, Ltd. We present the results of the temperature dependence of the Raman spectra of hexagonal HoMnO3 thin films in the 13–300 K temperature range. In addition to the usually observed phonon vibrations, we discovered several broad Raman scattering peaks, whose intensities change rapidly with temperature and disappear above the Néel temperature. Our analyses indicate that all the broad peaks are correlated with magnetic ordering, and we have assigned the origin of all the broad peaks.