Spin-manipulated phonon dynamics during magnetic phase transitions in triangular lattice antiferromagnet CuCr sub(1-x)Mg sub(x)O sub(2) semiconductor films

• Published in: RSC advances Vol. 6; no. 32; pp. 27136 - 27142
• Main Authors: Li, Xurui, Wang, Junyong, Zhang, Jinzhong, Li, Yawei, Hu, Zhigao, Chu, Junhao
• Format: Journal Article
• Language: English
• Published: 01.03.2016
• Subjects: Chromium; Doped films; Dynamics; Infrared; Magnetic transitions; Phonons; Red shift; Semiconductors
• ISSN: 2046-2069
• DOI: 10.1039/c6ra02881k

Raman scattering and infrared reflectance spectra of CuCr sub(1-x)Mg sub( x)O sub(2) films (x= 0.03, 0.06 and 0.09) in the temperature range of 5-300 K have been studied, combined with first-principles calculations. The abnormal redshift of the E sub(g) Raman mode center with decreasing temperature below 100 K for the lightly doped film (x= 0.03) is ascribed to the Cr 3d-O 2p-Cu 3d interaction. Strong disturbance of the local spin fluctuation at Cr sites in heavily Mg-doped films (x= 0.06 and 0.09) drives the E sub(g) mode center to a normal blueshift with decreasing temperature. With further decreasing temperature, the out-of-plane structure increases the internal spin-charge coupling. It enhances the spin-flip splitting and brings back the abnormal redshift of the E sub(g) Raman mode center. A similar but more obvious trend can be found from temperature-dependent E sub(u) infrared mode center shifts. Two successive magnetic transitions were observed at the corresponding Neel temperatures T sub(N1) around 24.7 K and T sub(N2) around 23.0 K, as manifested by magnetoresistance measurements. The interesting phenomena of phonon dynamics are suggested to be manipulated by the spin structures during the magnetic transitions.