Enhanced magnetocaloric properties of Erbium and Aluminum co-doped HoCrO3 orthochromite compound: An experimental and DFT study

Authors

• Jolaikha Sultana, College of Arts & Sciences
• Jemma R. DeFeo, Buffalo State University
• Rajiv K. Chouhan, Iowa State University
• Yenugonda Venkateswara, Buffalo State University
• Arjun K. Pathak, Buffalo State University
• Sanjay R. Mishra, College of Arts & Sciences

Abstract

This study investigates the microstructural and magnetocaloric characteristics of three orthochromite compounds: HoCrO3, Ho0.67Er0.33CrO3, and Ho0.67Er0.33Cr0.5Al0.5O3, synthesized via a sol-gel autocombustion method. X-ray diffraction confirmed a pure orthorhombic Pbnm structure in all samples. Replacing Ho³⁺ with Er³⁺ leads to a slight decrease in lattice constants due to their similar ionic radii. Substituting Cr³⁺ with the smaller Al³⁺ ion further reduces lattice parameters and unit cell volume. Density functional theory (DFT) calculations indicated that the G-type Antiferromagnetic (AFM-G) configuration is energetically stable for Ho0.75Er0.25CrO3 and HoCrO3, whereas the A-type Antiferromagnetic (AFM-A) configuration is the lowest energy state for Ho0.75Er0.25Cr0.5Al0.5O3. The energy difference between the most stable configuration and ferromagnetic configurations for Ho0.75Er0.25Cr0.5Al0.5O3, Ho0.75Er0.25CrO3, and HoCrO3 is 76.26, 251.07, and 235.42 meV/cell, respectively. It should be noted that adding Al³⁺ to the Cr³⁺ site significantly reduces the total energy gap (EAFM – EFM) in the HoCrO3 compound. This substitution also modified the Cr³⁺-O^2--Cr³⁺ bond angles and lengths, thereby affecting the magnetic and magnetocaloric characteristics of the materials. Temperature-dependent magnetization measurements indicated a reduction in the magnetic transition temperature because of doping, with temperatures decreasing from 141 K for HoCrO3 to 136 K for Ho0.67Er0.33CrO3 and 120 K for Ho0.67Er0.33Cr0.5Al0.5O3. The maximum magnetic entropy change, −ΔSm, determined from magnetic isotherms, increased with the substitution of Er³⁺ and Al³⁺. The −ΔSm observed for HoCrO3, Ho0.67Er0.33CrO3, and Ho0.67Er0.33Cr0.5Al0.5O3 was 6.46 Jkg⁻¹K⁻¹, 8.04 Jkg⁻¹K⁻¹, and 9.69 Jkg⁻¹K⁻¹, respectively at a 5T applied field, representing a 30 % enhancement in −ΔSm for Ho0.67Er0.33Cr0.5Al0.5O3 compared to the pure HoCrO3 compound.

Publication Title

Journal of Physics and Chemistry of Solids

Recommended Citation

Sultana, J., DeFeo, J., Chouhan, R., Venkateswara, Y., Pathak, A., & Mishra, S. (2025). Enhanced magnetocaloric properties of Erbium and Aluminum co-doped HoCrO3 orthochromite compound: An experimental and DFT study. Journal of Physics and Chemistry of Solids, 206 https://doi.org/10.1016/j.jpcs.2025.112856