A Datta, T Sarkar, M Roy-Chowdhury, P Tiwari, H Singh, J K Dey, S Thota
{"title":"锰取代铁磁性镍铬酸盐中可调能带隙和磁各向异性的演变","authors":"A Datta, T Sarkar, M Roy-Chowdhury, P Tiwari, H Singh, J K Dey, S Thota","doi":"10.1088/1361-648X/ad9537","DOIUrl":null,"url":null,"abstract":"<p><p>We report a detailed study on the composition (<i>x</i>) dependence of structural, electronic, magnetic, and optical studies of nickel chromate spinel (NiCr<sub>2</sub>O<sub>4</sub>) at various levels of Mn substitution at B sites. No significant structural distortion from cubic symmetry<i>Fd-</i>3m was noticed for all the compositions in the range 0 ⩽<i>x</i>⩽ 1 of Ni(Cr<sub>1-<i>x</i></sub>Mn<i><sub>x</sub></i>)<sub>2</sub>O<sub>4</sub>. However, there is significant alteration in the bond angles<i>∠</i>B<i>-</i>O<i>-</i>B (90.51°-93.86°) and<i>∠</i>A<i>-</i>O<i>-</i>B (122.48°-124.90°) (both of which follow completely opposite trend with increasing<i>x</i>) and bond lengths A<i>-</i>O (1.82-1.94 Å) and B<i>-</i>O (2.02-2.08 Å). The corresponding lattice parameter (<i>a</i>) follows Vegard's law (8.32 ± 0.001 Å ⩽<i>a</i>⩽ 8.45 ± 0.001Å). The electronic structure determined from the<i>x-</i>ray photoelectron spectroscopy reveals the divalent nature of Ni (with spin-orbit splitting energy Δ ∼ 17.62 eV). While the Cr and Mn are stable with trivalent electronic states having Δ<i>=</i>8 and 11.7 eV, respectively. These results are in consonance with the cationic distribution (Ni)<sub>A</sub>[(Cr<sub>1-<i>x</i></sub>Mn<i><sub>x</sub></i>)<sub>2</sub>]<sub>B</sub>O<sub>4</sub>obtained from the Rietveld refinement analysis. Interestingly, the current series shows a direct bandgap (<i>E</i><sub>G</sub>) semiconducting nature in which<i>E</i><sub>G</sub>varies from 1.16 to 2.40 eV within the range of<i>x</i>= 0.85-0. Such variation of<i>E</i><sub>G</sub>(<i>x</i>) is consistent with the compositional variation of the crystal structure data with anomalous change between<i>x</i>= 0.25 and 0.6. Beyond this range, the<i>E</i><sub>g</sub>mode (140 cm<sup>-1</sup>) in Raman spectra arising from Mn-O octahedral decreases continuously and vanishes at higher Mn concentrations. Our analysis shows that all the investigated compounds show long-range ferrimagnetic ordering below the Néel temperature,<i>T</i><sub>FN</sub>due to the unequal magnetic moments of the cations. However, both the ordering temperature<i>T</i><sub>FN</sub>and saturation magnetization (<i>M</i><sub>S</sub>) increases progressively from 73.3 K (1500 emu mol<sup>-1</sup>) to 116 K (3600 emu mol<sup>-1</sup>) with increasing the Mn content from 0 to 1, yet the maximum anisotropy (<i>H<sub>K</sub></i>~4.5 kOe,<i>K</i><sub>1</sub>~2.5 × 10<sup>4</sup>erg cc<sup>-1</sup>) shows an opposite trend with<i>x</i>. Such variation is ascribed to the altered magnetic superexchange interactions between the cations located at A and B sites following the trend<i>J</i><sub>BB</sub>><i>J</i><sub>AB</sub>><i>J</i><sub>AA</sub>, (<i>J</i><sub>BB</sub>/<i>k</i><sub>B</sub>=13.36 K).</p>","PeriodicalId":16776,"journal":{"name":"Journal of Physics: Condensed Matter","volume":" ","pages":""},"PeriodicalIF":2.3000,"publicationDate":"2024-12-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Evolution of tunable energy bandgap and magnetic anisotropy in Mn substituted ferrimagnetic nickel-chromates.\",\"authors\":\"A Datta, T Sarkar, M Roy-Chowdhury, P Tiwari, H Singh, J K Dey, S Thota\",\"doi\":\"10.1088/1361-648X/ad9537\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<p><p>We report a detailed study on the composition (<i>x</i>) dependence of structural, electronic, magnetic, and optical studies of nickel chromate spinel (NiCr<sub>2</sub>O<sub>4</sub>) at various levels of Mn substitution at B sites. No significant structural distortion from cubic symmetry<i>Fd-</i>3m was noticed for all the compositions in the range 0 ⩽<i>x</i>⩽ 1 of Ni(Cr<sub>1-<i>x</i></sub>Mn<i><sub>x</sub></i>)<sub>2</sub>O<sub>4</sub>. However, there is significant alteration in the bond angles<i>∠</i>B<i>-</i>O<i>-</i>B (90.51°-93.86°) and<i>∠</i>A<i>-</i>O<i>-</i>B (122.48°-124.90°) (both of which follow completely opposite trend with increasing<i>x</i>) and bond lengths A<i>-</i>O (1.82-1.94 Å) and B<i>-</i>O (2.02-2.08 Å). The corresponding lattice parameter (<i>a</i>) follows Vegard's law (8.32 ± 0.001 Å ⩽<i>a</i>⩽ 8.45 ± 0.001Å). The electronic structure determined from the<i>x-</i>ray photoelectron spectroscopy reveals the divalent nature of Ni (with spin-orbit splitting energy Δ ∼ 17.62 eV). While the Cr and Mn are stable with trivalent electronic states having Δ<i>=</i>8 and 11.7 eV, respectively. These results are in consonance with the cationic distribution (Ni)<sub>A</sub>[(Cr<sub>1-<i>x</i></sub>Mn<i><sub>x</sub></i>)<sub>2</sub>]<sub>B</sub>O<sub>4</sub>obtained from the Rietveld refinement analysis. Interestingly, the current series shows a direct bandgap (<i>E</i><sub>G</sub>) semiconducting nature in which<i>E</i><sub>G</sub>varies from 1.16 to 2.40 eV within the range of<i>x</i>= 0.85-0. Such variation of<i>E</i><sub>G</sub>(<i>x</i>) is consistent with the compositional variation of the crystal structure data with anomalous change between<i>x</i>= 0.25 and 0.6. Beyond this range, the<i>E</i><sub>g</sub>mode (140 cm<sup>-1</sup>) in Raman spectra arising from Mn-O octahedral decreases continuously and vanishes at higher Mn concentrations. Our analysis shows that all the investigated compounds show long-range ferrimagnetic ordering below the Néel temperature,<i>T</i><sub>FN</sub>due to the unequal magnetic moments of the cations. However, both the ordering temperature<i>T</i><sub>FN</sub>and saturation magnetization (<i>M</i><sub>S</sub>) increases progressively from 73.3 K (1500 emu mol<sup>-1</sup>) to 116 K (3600 emu mol<sup>-1</sup>) with increasing the Mn content from 0 to 1, yet the maximum anisotropy (<i>H<sub>K</sub></i>~4.5 kOe,<i>K</i><sub>1</sub>~2.5 × 10<sup>4</sup>erg cc<sup>-1</sup>) shows an opposite trend with<i>x</i>. Such variation is ascribed to the altered magnetic superexchange interactions between the cations located at A and B sites following the trend<i>J</i><sub>BB</sub>><i>J</i><sub>AB</sub>><i>J</i><sub>AA</sub>, (<i>J</i><sub>BB</sub>/<i>k</i><sub>B</sub>=13.36 K).</p>\",\"PeriodicalId\":16776,\"journal\":{\"name\":\"Journal of Physics: Condensed Matter\",\"volume\":\" \",\"pages\":\"\"},\"PeriodicalIF\":2.3000,\"publicationDate\":\"2024-12-03\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Journal of Physics: Condensed Matter\",\"FirstCategoryId\":\"101\",\"ListUrlMain\":\"https://doi.org/10.1088/1361-648X/ad9537\",\"RegionNum\":4,\"RegionCategory\":\"物理与天体物理\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q3\",\"JCRName\":\"PHYSICS, CONDENSED MATTER\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Physics: Condensed Matter","FirstCategoryId":"101","ListUrlMain":"https://doi.org/10.1088/1361-648X/ad9537","RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"PHYSICS, CONDENSED MATTER","Score":null,"Total":0}
Evolution of tunable energy bandgap and magnetic anisotropy in Mn substituted ferrimagnetic nickel-chromates.
We report a detailed study on the composition (x) dependence of structural, electronic, magnetic, and optical studies of nickel chromate spinel (NiCr2O4) at various levels of Mn substitution at B sites. No significant structural distortion from cubic symmetryFd-3m was noticed for all the compositions in the range 0 ⩽x⩽ 1 of Ni(Cr1-xMnx)2O4. However, there is significant alteration in the bond angles∠B-O-B (90.51°-93.86°) and∠A-O-B (122.48°-124.90°) (both of which follow completely opposite trend with increasingx) and bond lengths A-O (1.82-1.94 Å) and B-O (2.02-2.08 Å). The corresponding lattice parameter (a) follows Vegard's law (8.32 ± 0.001 Å ⩽a⩽ 8.45 ± 0.001Å). The electronic structure determined from thex-ray photoelectron spectroscopy reveals the divalent nature of Ni (with spin-orbit splitting energy Δ ∼ 17.62 eV). While the Cr and Mn are stable with trivalent electronic states having Δ=8 and 11.7 eV, respectively. These results are in consonance with the cationic distribution (Ni)A[(Cr1-xMnx)2]BO4obtained from the Rietveld refinement analysis. Interestingly, the current series shows a direct bandgap (EG) semiconducting nature in whichEGvaries from 1.16 to 2.40 eV within the range ofx= 0.85-0. Such variation ofEG(x) is consistent with the compositional variation of the crystal structure data with anomalous change betweenx= 0.25 and 0.6. Beyond this range, theEgmode (140 cm-1) in Raman spectra arising from Mn-O octahedral decreases continuously and vanishes at higher Mn concentrations. Our analysis shows that all the investigated compounds show long-range ferrimagnetic ordering below the Néel temperature,TFNdue to the unequal magnetic moments of the cations. However, both the ordering temperatureTFNand saturation magnetization (MS) increases progressively from 73.3 K (1500 emu mol-1) to 116 K (3600 emu mol-1) with increasing the Mn content from 0 to 1, yet the maximum anisotropy (HK~4.5 kOe,K1~2.5 × 104erg cc-1) shows an opposite trend withx. Such variation is ascribed to the altered magnetic superexchange interactions between the cations located at A and B sites following the trendJBB>JAB>JAA, (JBB/kB=13.36 K).
期刊介绍:
Journal of Physics: Condensed Matter covers the whole of condensed matter physics including soft condensed matter and nanostructures. Papers may report experimental, theoretical and simulation studies. Note that papers must contain fundamental condensed matter science: papers reporting methods of materials preparation or properties of materials without novel condensed matter content will not be accepted.