Internal friction and Jahn-Teller effect in the charge-ordered La1-xCaxMnO3 (0.5<x<0.87)

TL;DR

This study investigates how the Jahn-Teller effect influences the charge-ordered state, crystal structure, and magnetic properties of La1-xCaxMnO3 across a range of compositions, revealing a critical composition near x=0.75.

Contribution

It provides new experimental evidence linking Jahn-Teller distortions to structural and magnetic crossovers in La1-xCaxMnO3, highlighting their role in stabilizing the charge-ordered state.

Findings

Maximum electron-lattice interaction near x=0.75

Crossover from Q2 to Q3 Jahn-Teller mode at x=0.75

Structural change from tetragonal to orthorhombic at x=0.75

Abstract

The Jahn-Teller effect in the charge-ordered (CO) state for La1-xCaxMnO3 (0.5<x<0.87) was studied by measuring the low-temperature powder x-ray diffraction, internal friction, and shear modulus. We find that the electron-lattice interaction with the static Jahn-Teller distortion is the strongest near x=0.75 in the CO state. It was particularly observed that a crossover of the Jahn-Teller vibration mode from Q2 to Q3 near x=0.75 induces crossovers of the crystal structure from tetragonally compressed to tetragonally elongated orthorhombic, and of the magnetic structure from CE-type to C-type near x=0.75. The experimental results give strong evidence that the Jahn-Teller effect not only plays a key role in stabilizing the CO state, but also determines the magnetic and crystal structures in the CO state for La1-xCaxMnO3.