Revisiting La_0.5Sr_1.5MnO₄ lattice distortion and charge ordering with multi-beam resonant diffraction

Area of Science:

• Condensed Matter Physics
• Materials Science
• Crystallography

Background:

• La_0.5Sr_1.5MnO₄ exhibits complex phases at low temperatures.
• Understanding lattice distortions is crucial for its electronic properties.

Purpose of the Study:

• To observe and characterize sinusoidal wave-type distortions in La_0.5Sr_1.5MnO₄.
• To demonstrate the capability of multi-beam resonant X-ray diffraction (MRXD) for resolving distortion modes.
• To investigate charge disproportion between manganese sites.

Main Methods:

• Multi-beam resonant X-ray diffraction (MRXD) with (7/4 7/4 0) fractional primary diffraction.
• Measurement of two four-beam diffractions with opposite asymmetry at 6.5545 keV.
• Comparison with simulations based on dynamical X-ray diffraction theory.
• Analysis of MRXD profile sensitivity to incident X-ray energy near the Mn K edge.

Main Results:

• Observed sinusoidal wave-type distortions in the low-temperature orthorhombic phase of La_0.5Sr_1.5MnO₄.
• Demonstrated that MRXD can resolve distortion modes perpendicular to momentum transfer via a single azimuthal scan.
• Confirmed the sensitivity of MRXD to charge disproportion between manganese sites, indicating a small charge disproportion feature.

Conclusions:

• MRXD is a powerful technique for characterizing lattice distortions in materials.
• The study provides insights into the low-temperature phase of La_0.5Sr_1.5MnO₄.
• The findings contribute to understanding the relationship between structure and electronic properties in manganites.