A facile in situ reduction route for preparation of spinel CoCr₂O₄polycrystalline nanosheets and their magnetic properties

Electronic and magnetic properties of (1 1 1)-oriented CoCr2O4 epitaxial thin film

“…In Fig. 4(d), the magnitudes of the maximal XRMS values of Cr and Co at 15 K and 80 K are plotted as a function of applied magnetic field showing a saturation field of approximately 3 T. This is much larger than the reported bulk values 17,18,29 which are typically less than 0.6 T. This difference is attributed to the fact that in the bulk the magnetic field is commonly applied along the CCO [0 0 1] direction which is the spin easy axis.…”

“…As seen, Cr has two peaks at about 577 eV and 587 eV which correspond to the 2p 3/2 and 2p 1/2 peaks indicating Cr is in the trivalent state. 28,29 The 2p 3/2 and 2p 1/2 peaks of Co are at 781 eV and 797 eV indicating Co is in the divalent state 28,29 . In addition, no extra peaks from Cr 2+ , Cr 4+ or Co 3+ are observed, which excludes the possibility of a multivalent charge state.…”

Strongly Coupled CoCr 2 O 4 /Carbon Nanosheets as High Performance Electrocatalysts for Oxygen Evolution Reaction

“…For a meaningful comparison, pure nanoparticulate CoCr 2 O 4 (denoted as CoCr 2 O 4 ‐700) is synthesized at 700 °C using the same experimental procedure without carbon source. The high‐resolution Co 2 p (Figure S3, Supporting Information) and Cr 2 p spectra (Figure S4, Supporting Information) of CoCr 2 O 4 /CNS‐700 and CoCr 2 O 4 ‐700 are similar, which can be assigned as the states of divalent Co and trivalent Cr species, respectively . However, the surface oxygen states of the two samples are much different.…”

“…In a typical synthetic process, the metal–oleate (CoCr 2 (OH) x /OA) precursor (obtained by complexion of metal salts and sodium oleate; see the Experimental Section in the Supporting Information) is calcined with the molten‐salt (Na 2 SO 4 ) under Ar atmosphere. The X‐ray diffraction (XRD) pattern ( Figure a) of the as‐synthesized CoCr 2 O 4 /CNS‐700 product can be indexed as the cubic spinel phase of CoCr 2 O 4 crystal structure (JCPDS 80‐1668) . In addition, the Raman spectrum of CoCr 2 O 4 /CNS‐700 (Figure b) displays the pure CoCr 2 O 4 characteristic bands peaked at 189 ( F 2g ), 458 ( E g ), 517 ( F 2 g ), and 667 cm −1 ( A 1g ), which also support the formation of the cubic spinel phase of CoCr 2 O 4 .…”

Dispersible cobalt chromite nanoparticles: facile synthesis and size driven collapse of magnetism

“…Up to date, cobalt chromite NPs were prepared by sonochemistry 23 , thermolysis 24 , co-precipitation 15;16;25 , solgel method 26;27 , autocombustion 28;29 , solvothermal in situ reduction 30 and variants of the hydrothermal method 14;31;32 . In most of the above-described procedures, the as-prepared products were subjected to annealing at high temperatures in order to get nanocrystalline phase of the cobalt chromite.…”