Ferrimagnetic Co_1+δTe nanostructures

Direct evidence for the source of reported magnetic behavior in “CoTe”

“…3,15,18 The second issue concerns the source of the magnetism observed in recent studies on nanostructured CoTe x materials. [9][10][11][12][13] Wang et al 1 carried out high-resolution x-ray photoelectron spectroscopy (XPS) on cobalt telluride branched nanostructured samples. They observed weak satellite peaks in their Co 2p 3/2 /2p 1/2 spectra which they attribute to elemental Co. 1 Wu et al 5 observed second phase fcc Co peaks in their XRD patterns from carbon supported CoTe 1.20 nanoparticles; the second phase peaks were reduced for higher heat treatment temperatures.…”

“…11 A magnetic transition from paramagnetism to ferrimagnetism at approximately 40 K has been seen in Co-rich CoTe 0.79 nanostructures. 12 Finally, a very recent study reports weak ferromagnetism in 100 nm nanorods. 13 As discussed below, an explanation of the magnetic behavior for CoTe x follows from an understanding of the phase diagram and the nuclear magnetic resonance (NMR) results reported here.…”

“…However, there are still several recent reports in the literature of Co-Te nanostructured materials having the CoTe stoichiometry and being magnetic. [9][10][11][12][13] One such study reports CoTe nanowires a wells@phys.uconn.edu which exhibit ferrimagnetic behavior well above room temperature with a saturation magnetization of 0.2 µ B /Co. 10 Another report concerning CoTe nanotubes shows hysteresis loops with coercivity indicating ferromagnetic behavior.…”

“…In a later Mössbauer study, Fano and Ortalli [8] concluded that the stoichiometric composition CoTe does not exist. However, there are still several recent reports in the literature of Co-Te nanostructured materials having the CoTe stoichiometry and being magnetic [9][10][11][12][13]. One such study reports CoTe nanowires which exhibit ferrimagnetic behavior well above room temperature with a saturation magnetization of 0.2 μB/Co [10].…”

Structural, microstructural and magnetic characterization of the β-CoTe nanophase synthesized by a novel mechanochemical method

“…The inter-and intra-binding of Te-Te is short and furnished a low c/a ratio for the hexagonal cells. 13 The Seebeck coefficient is negative, also presenting a Curie-Weiss-like behavior for magnetic susceptibility 14,15 at high temperatures and hard ferrimagnetism at temperatures below 40 K. All these properties came from thermal synthesized materials, 11,16 in almost perfect bulk single crystals.…”