Synthesis and magnetic properties of some monotectic composites containing ultra-dispersed particles of YGdTbDyHo high-entropy alloy

Recent discoveries of low-dimensional and ultra-dispersed magnetocaloric materials revealed interesting results that help to uncover some fundamental aspects related to the magnetocaloric effect. One of the promising way to obtain ultra-fine metallic nanocomposites resistant to environmental conditions is the use alloy systems showing a liquid miscibility gap. Within this study we fabricate some monotectic composites containing YGdTbDyHo high-entropy alloy and examine their structure, microstructure, thermal conductivity, magnetic and magnetocaloric properties, employing X-ray diffraction, electron microscopy, magnetometry and ab initio molecular dynamics simulations. The results reveal that the use of chromium, vanadium and their mutual alloys as a host monotectic matrix in combination with standard arc-melting enables the YGdTbDyHo high-entropy alloy to be evenly dispersed in the form of small irregularly-shaped particles (droplets or lamellae) of less than 1–2 μm in size, practically uncontaminated with the host metal in which these inclusions are distributed. The monotectic composites have increased Neel points, but reduced magnetocaloric response compared to non-dispersed as-cast YGdTbDyHo alloy. The observed tendencies in the behavior of magnetic properties of the developed monotectic alloys turned out to be similar to the micron powders and thin films based on rare-earth metals studied to date, i.e. the effects of micro- and nanostructuring in all systems are of the same nature and play a decisive role in their magnetism. The study results allow us to conclude that using immiscible metals in alloy fabrication process is effectient for dispersing rare-earth high entropy alloys and opens up new prospects in designing low-dimensional and nanoscale magnetic phases with adjustable magnetocaloric properties.