Jahn-teller dynamics in charge-ordered manganites from raman spectroscopy

Area of Science:

• Condensed Matter Physics
• Materials Science
• Spectroscopy

Background:

• Manganites like Pr0.65Ca0.35MnO3 exhibit complex charge ordering and magnetic behaviors.
• Understanding the interplay between charge, spin, and lattice is crucial for materials science.
• Raman spectroscopy is a powerful tool for probing lattice dynamics and electronic interactions.

Purpose of the Study:

• To investigate the charge-lattice and spin-lattice couplings in Pr0.65Ca0.35MnO3.
• To correlate Raman spectral changes with temperature-dependent charge ordering and magnetic transitions.
• To explore the influence of excitation energy on the observed spectral features.

Main Methods:

• Raman spectroscopy measurements as a function of temperature.
• Variable excitation energy Raman spectroscopy.
• Comparison with magnetic moment and electrical conductivity data.

Main Results:

• Charge ordering (T(co) ≈ 225 K) and antiferromagnetic transitions (T(N) ≈ 175 K) significantly alter Raman spectra.
• Evidence of strong charge-lattice and spin-lattice couplings observed.
• A transition from dynamic to static Jahn-Teller distortions occurs below T(co).
• A spectral change above 2.5 eV excitation energy is attributed to resonant polaron excitation.

Conclusions:

• Raman spectra provide insights into the coupled electronic and structural properties of manganites.
• The study highlights the sensitivity of Raman spectroscopy to phase transitions and electron-lattice interactions.
• Polaron dynamics play a role in the optical properties of Pr0.65Ca0.35MnO3 at higher excitation energies.