Substitutional defect engineering in gadolinium garnets, Gd3-xMʹxFe5O12 (Mʹ = Pr3+ (x = 0.8) and Ca2+ (x = 0.5)): A structural and magnetocaloric study

Authors

• Jolaikha Sultana, College of Arts & Sciences
• Jacob Casey, Buffalo State University
• Yenugonda Venkateswara, Buffalo State University
• Romakanta Bhattarai, School of Science
• Arjun K. Pathak, Buffalo State University
• Felio Perez, University of Memphis
• X. Shen, College of Arts & Sciences
• Sanjay R. Mishra, College of Arts & Sciences

Abstract

We report the structural, magnetic, and magnetocaloric properties of substitutional defect-engineered Gd3-xMʹxFe5O12 garnet compound (Mʹ = Pr³⁺ (x = 0.8) and Ca²⁺ (x = 0.5)). X-ray powder diffraction shows all samples have cubic crystal structure with space group Ia 3‾ d. Mössbauer spectroscopy revealed the presence of an increased paramagnetic phase in the Ca²⁺-doped Gd2.5Ca0.5Fe5O12 garnet, compared to a pristine and Pr³⁺-doped Gd2.2Pr0.8Fe5O12. A paramagnetic phase in the Ca²⁺-doped Gd2.5Ca0.5Fe5O12 garnet is attributed to Ca²⁺ doping, which changes Fe³⁺ to Fe⁴⁺ to maintain electroneutrality in the compound. According to a DFT study, doping with either Ca²⁺ or Pr³⁺ ions decreases the compound's overall magnetic moment compared to the pristine Gd3Fe5O12 compound and more so for the Pr³⁺-doped Gd3Fe5O12 due to the antiferromagnetic coupling of Pr³⁺ with Gd^3+. The maximum magnetic entropy change, ΔSmax, estimated from isothermal magnetization data, was observed to be 3.80 Jkg⁻¹K⁻¹ (Tmax = 37.5K), 2.33 Jkg⁻¹K⁻¹ (Tmax = 52.5K), and 3.11 Jkg⁻¹K⁻¹ (Tmax = 42.5K) for Gd3Fe5O12, Gd2.2Pr0.8Fe5O12, and Gd2.5Ca0.5Fe5O12, respectively under 5T field and their respective relative cooling power, RCP, at the same magnetic field, are 380 J kg⁻¹, 263 J kg⁻¹, and 349 J kg⁻¹. These results show that doping with a magnetic Pr3+ and non-magnetic Ca2+ significantly affects the magnetic entropy changes and cooling capacity in Gd3Fe5O12, demonstrating that substitutional defect engineering can influence its magnetocaloric properties over a wider temperature range.

Publication Title

Ceramics International

Recommended Citation

Sultana, J., Casey, J., Venkateswara, Y., Bhattarai, R., Pathak, A., Perez, F., Shen, X., & Mishra, S. (2025). Substitutional defect engineering in gadolinium garnets, Gd3-xMʹxFe5O12 (Mʹ = Pr3+ (x = 0.8) and Ca2+ (x = 0.5)): A structural and magnetocaloric study. Ceramics International, 51 (19), 28524-28536. https://doi.org/10.1016/j.ceramint.2025.04.062