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- Nayak, S., et al.
(författare)
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Magnetic compensation, field-dependent magnetization reversal, and complex magnetic ordering in Co2TiO4
- 2015
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 92:21
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Tidskriftsartikel (refereegranskat)abstract
- The complex nature of magnetic ordering in the spinel Co2TiO4 is investigated by analyzing the temperature and magnetic field dependence of its magnetization (M), specific heat (C-p), and ac magnetic susceptibilities chi' and chi ''. X-ray diffraction of the sample synthesized by the solid-state reaction route confirmed the spinel structure whereas x-ray photoelectron spectroscopy shows its electronic structure to be Co2TiO4 = [Co2+][Co3+ Ti3+]O-4. From analysis of the temperature dependence of the dc paramagnetic susceptibility, the magnetic moments mu(A) = 3.87 mu(B) and mu(B) = 5.19 mu B on the A and B sites are determined with mu(B) in turn yielding mu(Ti3+) = 1.73 mu(B) and mu(Co3+) = 4.89 mu(B). Analysis of the dc and ac susceptibilities combined with the weak anomalies observed in the C-p vs T data shows the existence of a quasi-long-range ferrimagnetic state below T-N similar to 47.8K and a compensation temperature T-comp similar to 32 K, the latter characterized by sign reversal of magnetization with its magnitude depending on the applied magnetic field and the cooling protocol. Analysis of the temperature dependence of M (field cooled) and M (zero field cooled) data and the hysteresis loop parameters is interpreted in terms of large spin clusters. These results in Co2TiO4, significantly different from those reported recently in isostructural Co2SnO4 = [Co2+][Co2+ Sn4+]O-4, warrant further investigations of its magnetic structure using neutron diffraction.
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| 2. |
- Nayak, S., et al.
(författare)
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Low-temperature anomalous magnetic behavior of Co2TiO4 and Co2SnO4
- 2016
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 120:16
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Tidskriftsartikel (refereegranskat)abstract
- We report the low-temperature anomalous magnetic behavior of ferrimagnetic spinels cobalt orthotitanate (Co2TiO4), which exhibits magnetic compensation behavior across 31.74 K, and cobalt orthostannate (Co2SnO4) exhibiting two sequential magnetic transitions, namely (i) ferrimagnetic to paramagnetic transition with Neel temperature T-N similar to 41 K and reentrant spin-glass behavior with glass transition temperature T-SG similar to 39 K. The Arrott plot (H/M versus M-2) criterion has been used to extricate the order of sequential magnetic transitions occurring below TN. Negative slopes of the Arrott plots below 32 K, metamagnetic-like character of the M-H isotherms, anomalies in the specific-heat (C-P T-1 versus T) below 15 K, and a zero-crossover of isothermal magnetic-entropychange (Delta S) signify the presence of pseudo first-order discontinuous magnetic phase transition in the low-temperature regime 5K <= T <= 32 K. The dc- and ac-susceptibilities of both Co2TiO4 and Co2SnO4 are interpreted in terms of frozen-spin-clusters, which are responsible for very large magnitudes of the coercivity H-C similar to 20 kOe and bipolar-exchange bias H-EB similar to -20 kOe observed below 10 K.
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