We have synthesized unique colloidal nanoplatelets of the ferromagnetic twodimensional (2D) van der Waals material CrI 3 and have characterized these nanoplatelets structurally, magnetically, and by magnetic circular dichroism spectroscopy. The isolated CrI 3 nanoplatelets have lateral dimensions of ~25 nm and ensemble thicknesses of only ~4 nm, corresponding to just a few CrI 3 monolayers. Magnetic and magneto-optical measurements demonstrate robust 2D ferromagnetic ordering in these nanoplatelets with Curie temperatures similar to those observed in bulk CrI 3 , despite the strong spatial confinement. These data also show magnetization steps akin to those observed in micron-sized few-layer 2D sheets and associated with concerted spin-reversal of individual CrI 3 layers within few-layer van der Waals stacks. Similar data have also been obtained for CrBr 3 and anion-alloyed Cr(I 1-x Br x ) 3 nanoplatelets. These results represent the first example of laterally confined 2D van der Waals ferromagnets of any composition. The demonstration of robust ferromagnetism at nanometer lateral dimensions opens new doors for miniaturization in spintronics devices based on van der Waals ferromagnets.
Materials science research has expanded significantly
in recent
years; a multidisciplinary field, home to an ever-growing number of
chemists. However, our general chemistry degree courses have not changed
to reflect the rise in interest in this topic. In this paper, we propose
a laboratory experiment for the undergraduate chemistry practical
course, which may serve as a hands-on introduction to this field.
The experiment involves the synthesis and characterization of magnetic
materials via commonly employed techniques in materials science. Students
begin by producing three metal ferrite spinels using a sol–gel
combustion synthesis. They must then characterize the differing magnetic
properties across their three samples using a magnetic susceptibility
balance. In the second part of the experiment, students must create
a ferrofluid via coprecipitation, from which they may observe the
phenomenon of “spiking” in response to an external magnet.
Additional data such as X-ray diffraction (XRD) patterns and transmission
electron microscopy (TEM) images corresponding to these materials
are also provided, and students are tasked with the interpretation
of these data in their writeup report. Upon completion, students should
gain a new-found understanding of materials science and its fundamental
overlap with chemistry.
Titanium dioxide, or titania, is perhaps the most well-known and widely studied photocatalytic material, with myriad applications, due to a high degree of tunability achievable through the incorporation of dopants...
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