Near‐Infrared d–d Transitions of NiI₂, CdI₂:Ni²⁺, and CoI₂

Abstract

The absorption spectra of KIz, CdI,:Ni2+, and CoI, in the wave-number region 4000 to 16000 cm-l are reported. The spectra are interpreted in terms of d-d transitions of NiZ+ and Co2+ ions. Parameters of the electron repulsion, cubic crystal field, and spin-orbit coupling are estimated. From the latter the transferred spin densities are deduced and compared with Mossbauer data. Birefringence experiments as a function of the temperature show the presence of two phase transitions in XI,.Nous avons mesure les spectres d'absorption de NiI,, CdI,:Ni2+ et CoI, dans la region de 4000 B 16000 em-l. Les spectres ont Ate interpret6 comme transitions d-d des ions Ni2+ et Co2+. A partir des spectres on a determine les parametres de la repulsion interelectronique, du champ cristailin cubique et de la couplage spin-orbite. La densite de spin sup l'ion de iode est calcule et comparu avec le spectre Mossbauer. Experiments de la refraction double en fonction de la temperature montrent la presence de deux transitions de phase dans NiI,.

Dual-Color Lasing Lines from EMPs in Diluted Magnetic Semiconductor CdS:NiI Structure

“…Samples A and B show only two emission bands, one lying at near bandedge (NBE) and the other lies at the near infrared (NIR) region. The former comes from FX+EMP, while the latter should come from d-d transition of Ni ion and (NiX) n (X = S or F and Cl, n ≥ 2) [32, 33, 43]. In contrast, sample C shows three emission bands, two bands lying at NBE region and one at NIR region.…”

“…Its assignment is reasonable here that the self-trapped exciton component by independent I − ion should have more contribution and a lower energy than Br − in NiBr 2 doping system because I − could be more easily reduced and easily deposited than Br − in CdS lattice. The broadband at about 644 nm should contain the d-d transitions of Ni ions [32, 33, 43] and their aggregates due to its very broad width. We also found a 773 nm band but has a very low ratio, which should be due to the magnetic polaron pair.…”

“…The photoluminescence of NiX 2 compounds comes from their absorption if it could occur. NiF 2 [49], NiCl 2 , NiBr 2 [33], and NiI 2 [43] crystals show very similar absorption profiles due to their Ni(II) d-d transition in the range of 600-800 nm, over which there is an extended charge-transfer (CT) absorption bandedge for only NiI 2 shifted to 900 nm, superposed with the d-d transition bands. The gas-phase absorption spectra of NiCl 2 and NiBr 2 also show similar absorption profile in this 600-800 nm range while the NiI 2 have no strong absorption in this zone but even lower energy zone [49].…”

NIR-VIS reflectivity spectra of some transition metal thiophosphates

“…In fact, 4Txg(F) is split by the spin-orbit interaction in a doublet E~, followed by a quartet U~ and a sextet E~ + U~, while 4T2g (F) is split in a quartet U~, in a doublet E~ and in a sextet E~+U~ [26,6]. Thus the observed narrow peak at 1.08eV and the shoulder at 1.15 eV arise probably from a splitting due to spin-orbit coupling [29] of the spin-allowed interconfigurational transitions (with k = 1) 4Tlg (F) --) 4T2g (F) (see transitions I and II in fig. 8).…”

Tunable spin-polarized band gap in Si2/NiI2 vdW heterostructure

“…29,30,32 The magnetic structure of the bulk NiI 2 was determined by neutron diffraction, with spins ordered ferromagnetically in each Ni 2+ ion and a magnetic moment of 1.6 m B (ref. 42), and for a single layer the calculated magnetic moment is 2 m B . 43 In our calculations, the magnetic ordering of the NiI 2 single layer is determined by increasing the size of the unit cell (supercell with 12 atoms).…”