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Manganites; Jahn-Teller distortion; Raman scattering; phonon; spin excitation; spin-phonon coupling; electronic Raman scattering

Raman scattering experiments have been carried out on single crystals of Nd_0.5Sr_0.5MnO₃ as a function of temperature in the range of 320–50 K, covering the paramagnetic insulator-ferromagnetic metal transition at 250 K and the charge-ordering antiferromagnetic transition at 150 K. The diffusive electronic Raman scattering response is seen in the paramagnetic phase which continue to exist even in the ferromagnetic phase, eventually disappearing below 150 K. We understand the existence of diffusive response in the ferromagnetic phase to the coexistence of the different electronic phases. The frequency and linewidth of the phonons across the transitions show significant changes, which cannot be accounted for only by anharmonic interactions.

Md Motin Seikh^{1 2} A K Sood^{1 3} Chandrabhas Narayana¹

1. Chemistry and Physics of Materials Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur P.O., Bangalore - 560 064, India
2. Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore - 560 012, India
3. Department of Physics, Indian Institute of Science, Bangalore - 560 012, India

Published

January 2005

Manuscript received

31 May 2004

Manuscript revised

25 October 2004

Accepted

29 October 2004