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

IF 4.3 3区材料科学 Q2 CHEMISTRY, MULTIDISCIPLINARY

Journal of Physics and Chemistry of Solids Pub Date : 2025-05-13 DOI:10.1016/j.jpcs.2025.112856

Jolaikha Sultana , Jemma R. DeFeo , Rajiv K. Chouhan , Yenugonda Venkateswara , Arjun K. Pathak , Sanjay R. Mishra

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Abstract

This study investigates the microstructural and magnetocaloric characteristics of three orthochromite compounds: HoCrO₃, Ho_0.67Er_0.33CrO₃, and Ho_0.67Er_0.33Cr_0.5Al_0.5O₃, 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 Ho_0.75Er_0.25CrO₃ and HoCrO₃, whereas the A-type Antiferromagnetic (AFM-A) configuration is the lowest energy state for Ho_0.75Er_0.25Cr_0.5Al_0.5O₃. The energy difference between the most stable configuration and ferromagnetic configurations for Ho_0.75Er_0.25Cr_0.5Al_0.5O₃, Ho_0.75Er_0.25CrO_3, 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 (E_AFM – E_FM) 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 Ho_0.67Er_0.33CrO₃ and 120 K for Ho_0.67Er_0.33Cr_0.5Al_0.5O₃. The maximum magnetic entropy change, −ΔS_m, determined from magnetic isotherms, increased with the substitution of Er³⁺ and Al³⁺. The −ΔS_m observed for HoCrO₃, Ho_0.67Er_0.33CrO_3, and Ho_0.67Er_0.33Cr_0.5Al_0.5O₃ 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 −ΔS_m for Ho_0.67Er_0.33Cr_0.5Al_0.5O₃ compared to the pure HoCrO₃ compound.

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铒和铝共掺杂HoCrO3正铬铁矿化合物的增强磁热性能：实验和DFT研究

研究了溶胶-凝胶自燃烧法制备的三种正铬铁矿化合物HoCrO3、Ho0.67Er0.33CrO3和Ho0.67Er0.33Cr0.5Al0.5O3的微观结构和磁热特性。x射线衍射证实所有样品均为纯正交pnm结构。用Er3+代替Ho3+，由于其离子半径相似，晶格常数略有下降。用较小的Al3+离子取代Cr3+进一步减小了晶格参数和单元胞体积。密度泛泛理论（DFT）计算表明，Ho0.75Er0.25CrO3和HoCrO3的g型反铁磁（AFM-G）构型能量稳定，而Ho0.75Er0.25Cr0.5Al0.5O3的a型反铁磁（AFM-A）构型能量最低。Ho0.75Er0.25Cr0.5Al0.5O3、Ho0.75Er0.25CrO3和HoCrO3的最稳定构型与铁磁构型的能量差分别为76.26、251.07和235.42 meV/cell。值得注意的是，在Cr3+位点上加入Al3+可以显著降低HoCrO3化合物的总能隙（EAFM - EFM）。这种取代还改变了Cr3+-O2—Cr3+键的角度和长度，从而影响了材料的磁性和磁热特性。温度相关磁化测量表明，由于掺杂，磁转变温度降低，HoCrO3的温度从141 K降至136 K， Ho0.67Er0.33Cr0.5Al0.5O3的温度降至120 K。根据磁等温线测定的最大磁熵变化为−ΔSm，随着Er3+和Al3+的取代而增加。在5T电场下，HoCrO3、Ho0.67Er0.33CrO3和Ho0.67Er0.33Cr0.5Al0.5O3的- ΔSm分别为6.46 Jkg−1K−1、8.04 Jkg−1K−1和9.69 Jkg−1K−1，与纯HoCrO3化合物相比，Ho0.67Er0.33Cr0.5Al0.5O3的- ΔSm提高了30%。

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来源期刊

Journal of Physics and Chemistry of Solids 工程技术-化学综合

CiteScore

7.80

自引率

2.50%

发文量

605

审稿时长

40 days

期刊介绍： The Journal of Physics and Chemistry of Solids is a well-established international medium for publication of archival research in condensed matter and materials sciences. Areas of interest broadly include experimental and theoretical research on electronic, magnetic, spectroscopic and structural properties as well as the statistical mechanics and thermodynamics of materials. The focus is on gaining physical and chemical insight into the properties and potential applications of condensed matter systems. Within the broad scope of the journal, beyond regular contributions, the editors have identified submissions in the following areas of physics and chemistry of solids to be of special current interest to the journal: Low-dimensional systems Exotic states of quantum electron matter including topological phases Energy conversion and storage Interfaces, nanoparticles and catalysts.