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Magnetic ground state and exchange interactions in the Ising chain ferromagnet CoNb2O6
Citation
Thota, Subhash, Ghosh, Sayandeep, R., Maruthi, Joshi, D. C., Medwal, Rohit, Rawat, Rajdeep Singh, & Seehra, Mohindar S. (2021). Magnetic ground state and exchange interactions in the Ising chain ferromagnet Co Nb 2 O 6. Physical Review B, 103, Article 064415. https://doi.org/10.1103/PhysRevB.103.064415
Author
Thota, Subhash
•
Ghosh, Sayandeep
•
Maruthi, R.
•
Joshi, Deep C.
•
Medwal, Rohit
•
•
Seehra, Mohindar Singh
Abstract
Reported here are measurements and analysis of the magnetization (M) versus temperature (1.9–400 K) in magnetic fields H up to 90 kOe for a polycrystalline sample of Ising chain ferromagnet Co Nb2 O6 with TC = 2.9K. For T > TC, the fit of magnetic susceptibility χ = M /H (H = 300 Oe) to χ = χ0 + C / (T−Θ) with χ0 = 0.0009 emu mol–1 Oe–1 determined from high -T data yields Θ = 11K and magnetic moment μ = 4.994μB per Co2+ ion calculated from experimental C = 3.12 emu K mol–1 Oe–1. Values of g obtained from μ2 / μB2 = g2S (S + 1) for spin S = 1/2 and 3/2 are used to determine μZ = g S μB and compared with μZ obtained from saturation magnetization and neutron diffraction for T ≪ TC. This analysis of the data for both above and below TC shows that the ground state of Co2+ in Co Nb2 O6 has the effective spin S = 1/2 and not S = 3/2 expected from Hund's rules, the S = 1/2 ground state resulting from the combined effects of a noncubic crystalline field and spin-orbit coupling. The fit of the data for T > TC to χ = χ0 + (C/T) exp (J0 / 2kBT) valid for an Ising chain with S = 1/2 yields the intrachain ferromagnetic exchange constant J0 / kB = 6.2K, whereas the g value with S = 1/2 and the experimental critical fields for spin flips yields interchain antiferromagnetic exchange constants J1 / kB = −0.42K and J2 / kB = − 0.67K.
Date Issued
2021
Journal
Physical Review B
DOI
10.1103/PhysRevB.103.064415