Colloids consisting of the CoCrCuFeNi high-entropy alloy nanoparticles in ionic liquid
with the 1-butyl-3-methylimidazolium ([BMIM]+) cation and the tetrafluorborate ([BF4]-)
anion were obtained by the DC magnetron sputtering of high-entropy alloy target in
vacuum, onto the surface of [BMIM.BF4] ionic liquid. The method of the nanoparticle
colloid preparation is based on negligibly small vapour pressure of the ionic liquid,
which allows its application in vacuum. The high-entropy alloy nanoparticle colloids
were studied by HRTEM microscopy and SQUID magnetometry. Results of the structural
and magnetic analyses show that the colloids contain ultra-small single-crystalline
nanoparticles of an uneven shape and typical size of (2−3) nm. The nanoparticles have
relatively narrow size distribution which is typical for this preparation method.
The high-entropy alloy nanocolloids show complex magnetic properties that are a function
of temperature, applied magnetic field and mass content of the nanoparticles in the
colloids. The obtained results imply significant magnetic interactions between the
ionic liquid and the high-entropy alloy nanoparticles.
