Akshay Kumar, Jong Woo Kim, Mohit K. Sharma, Kavita Kumari, Ankush Vij, B. Koo
{"title":"铌改性 La1.4Sr1.6Mn2-xNbxO7(0.0 ≤ x ≤ 0.15)层状过氧化物中巨大制冷剂容量的证据","authors":"Akshay Kumar, Jong Woo Kim, Mohit K. Sharma, Kavita Kumari, Ankush Vij, B. Koo","doi":"10.3390/magnetochemistry10040022","DOIUrl":null,"url":null,"abstract":"In this work, evidence of isothermal magnetic entropy change (∆SM) over a broad temperature region is presented in a series of La1.4Sr1.6Mn2−xNbxO7 Ruddlesden–Popper compounds with niobium modification (Nb) (0.0 ≤ x ≤ 0.15) at the manganese (Mn) site. The ceramic samples were obtained through a solid-state sintering method in optimized conditions. All compounds predominantly possessed Ruddlesden–Popper phase while a few additional reflections were resolved in Nb-doped compounds which indicates the separation of structural phases. These peaks are assigned to a separate layered perovskite and single perovskite with tetragonal symmetry and hexagonal symmetry, respectively. The microstructure of the pure sample reveals uniform grain morphology but in Nb-doped specimens chiefly three types of grains were found. It was assumed that the inter-connected large particles were of R-P phase which is dominant in both parent and x = 0.05 compounds, while the hexagonal and polygonal morphology of grains in higher concentrations of dopants directly corroborates with the symmetry of single perovskite and additional layered perovskite phases, respectively. The parent compound exhibits a single ∆SM curve, whereas all Nb-substituted samples display bifurcated ∆SM curves. This indicated two transition regions with multiple magnetic components, attributed to distinct structural phases. The highest ∆SM values obtained for components corresponding to the R-P phase are 2.32 Jkg−1k−1, 0.75 Jkg−1k−1, 0.58 Jkg−1k−1 and 0.43 Jkg−1k−1 and for the second component located around room temperature are 0.0 Jkg−1k−1, 0.2 Jkg−1k−1, 0.28 Jkg−1k−1 and 0.35 Jkg−1k−1 for x = 0.0, 0.05, 0.10 and 0.15 compositions, respectively, at 2.5 T. Due to the collective participation of both components the ∆SM was expanded through a broad temperature range upon Nb doping.","PeriodicalId":18194,"journal":{"name":"Magnetochemistry","volume":null,"pages":null},"PeriodicalIF":2.6000,"publicationDate":"2024-03-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Evidence of a Large Refrigerant Capacity in Nb-Modified La1.4Sr1.6Mn2−xNbxO7 (0.0 ≤ x ≤ 0.15) Layered Perovskites\",\"authors\":\"Akshay Kumar, Jong Woo Kim, Mohit K. Sharma, Kavita Kumari, Ankush Vij, B. Koo\",\"doi\":\"10.3390/magnetochemistry10040022\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"In this work, evidence of isothermal magnetic entropy change (∆SM) over a broad temperature region is presented in a series of La1.4Sr1.6Mn2−xNbxO7 Ruddlesden–Popper compounds with niobium modification (Nb) (0.0 ≤ x ≤ 0.15) at the manganese (Mn) site. The ceramic samples were obtained through a solid-state sintering method in optimized conditions. All compounds predominantly possessed Ruddlesden–Popper phase while a few additional reflections were resolved in Nb-doped compounds which indicates the separation of structural phases. These peaks are assigned to a separate layered perovskite and single perovskite with tetragonal symmetry and hexagonal symmetry, respectively. The microstructure of the pure sample reveals uniform grain morphology but in Nb-doped specimens chiefly three types of grains were found. It was assumed that the inter-connected large particles were of R-P phase which is dominant in both parent and x = 0.05 compounds, while the hexagonal and polygonal morphology of grains in higher concentrations of dopants directly corroborates with the symmetry of single perovskite and additional layered perovskite phases, respectively. The parent compound exhibits a single ∆SM curve, whereas all Nb-substituted samples display bifurcated ∆SM curves. This indicated two transition regions with multiple magnetic components, attributed to distinct structural phases. The highest ∆SM values obtained for components corresponding to the R-P phase are 2.32 Jkg−1k−1, 0.75 Jkg−1k−1, 0.58 Jkg−1k−1 and 0.43 Jkg−1k−1 and for the second component located around room temperature are 0.0 Jkg−1k−1, 0.2 Jkg−1k−1, 0.28 Jkg−1k−1 and 0.35 Jkg−1k−1 for x = 0.0, 0.05, 0.10 and 0.15 compositions, respectively, at 2.5 T. 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Evidence of a Large Refrigerant Capacity in Nb-Modified La1.4Sr1.6Mn2−xNbxO7 (0.0 ≤ x ≤ 0.15) Layered Perovskites
In this work, evidence of isothermal magnetic entropy change (∆SM) over a broad temperature region is presented in a series of La1.4Sr1.6Mn2−xNbxO7 Ruddlesden–Popper compounds with niobium modification (Nb) (0.0 ≤ x ≤ 0.15) at the manganese (Mn) site. The ceramic samples were obtained through a solid-state sintering method in optimized conditions. All compounds predominantly possessed Ruddlesden–Popper phase while a few additional reflections were resolved in Nb-doped compounds which indicates the separation of structural phases. These peaks are assigned to a separate layered perovskite and single perovskite with tetragonal symmetry and hexagonal symmetry, respectively. The microstructure of the pure sample reveals uniform grain morphology but in Nb-doped specimens chiefly three types of grains were found. It was assumed that the inter-connected large particles were of R-P phase which is dominant in both parent and x = 0.05 compounds, while the hexagonal and polygonal morphology of grains in higher concentrations of dopants directly corroborates with the symmetry of single perovskite and additional layered perovskite phases, respectively. The parent compound exhibits a single ∆SM curve, whereas all Nb-substituted samples display bifurcated ∆SM curves. This indicated two transition regions with multiple magnetic components, attributed to distinct structural phases. The highest ∆SM values obtained for components corresponding to the R-P phase are 2.32 Jkg−1k−1, 0.75 Jkg−1k−1, 0.58 Jkg−1k−1 and 0.43 Jkg−1k−1 and for the second component located around room temperature are 0.0 Jkg−1k−1, 0.2 Jkg−1k−1, 0.28 Jkg−1k−1 and 0.35 Jkg−1k−1 for x = 0.0, 0.05, 0.10 and 0.15 compositions, respectively, at 2.5 T. Due to the collective participation of both components the ∆SM was expanded through a broad temperature range upon Nb doping.
期刊介绍:
Magnetochemistry (ISSN 2312-7481) is a unique international, scientific open access journal on molecular magnetism, the relationship between chemical structure and magnetism and magnetic materials. Magnetochemistry publishes research articles, short communications and reviews. Our aim is to encourage scientists to publish their experimental and theoretical results in as much detail as possible. Therefore, there is no restriction on the length of the papers. The full experimental details must be provided so that the results can be reproduced.