HoCrO3 and YCrO3: a comparative study.

Area of Science:

• Solid State Chemistry
• Materials Science
• Magnetism

Background:

• Orthorhombic perovskite-like compounds (AcrO3) exhibit complex magnetic and optical properties.
• Holmium chromate (HoCrO3) contains a magnetic Ho(3+) ion, while Yttrium chromate (YCrO3) has a non-magnetic Y(3+) ion.
• Both Ho(3+) and Y(3+) possess identical ionic radii, allowing for direct comparison of magnetic effects.

Purpose of the Study:

• To comparatively investigate the structural, optical, and magnetic properties of isostructural HoCrO3 and YCrO3.
• To understand the influence of the Ho(3+) local magnetic field on the magnetic ordering of Cr(3+) ions.
• To elucidate electron correlation effects in these systems using various experimental techniques.

Main Methods:

• X-ray diffraction for structural parameter analysis.
• Low-wavenumber Raman spectroscopy to study phonon modes.
• Diffuse reflectance spectroscopy to probe optical transitions of Cr ions.
• DC magnetization measurements (5-300 K) and isotherm analysis.

Main Results:

• Identical structural parameters were observed for both HoCrO3 and YCrO3.
• Significant differences in low-wavenumber Raman active phonon modes were detected.
• Cr(3+) magnetic ordering temperature is insensitive to the Ho(3+) local field but sensitive to thermal cycling under an external magnetic field.
• Thermal hysteresis indicates magnetic disorder near the phase transition, linked to weak ferromagnetism and/or structural distortions.

Conclusions:

• The magnetic ordering of Cr(3+) in ACrO3 is primarily governed by factors other than the local Ho(3+) magnetic field.
• Structural distortions and weak ferromagnetism play a crucial role in the observed magnetic behavior and thermal hysteresis.
• This study provides insights into the interplay between magnetic ions and lattice properties in perovskite-like structures.