Dopant-induced spin control in nanocrystals for strong permanent magnets and other magnetic devices

Abstract

Over the last three decades, the synthesis and applications of quantum dots have emerged as prominent areas of scientific research. The discovery of quantum dots was awarded the Nobel Prize in Chemistry in 2023. In this article, we review the luminescence and magnetic properties of doped quantum dots. The incorporation of a dopant in a quantum dot in the size range between 5 and 20 nm has been shown to polarize spins of the dopant due to quantum confinement. Next, the polarized dopant spins induce concurrent alignment of spins of the paramagnetic quantum dot and thereby convert it to ferromagnetic nanocrystals. The nanocomposite of these doped ferromagnetic nanocrystals (hard) and undoped paramagnetic nanocrystals (soft), when densified, is expected to yield strong permanent magnets based on theoretical prediction. Besides creating permanent magnets, the dopant-induced control of spin polarization of nanocrystals is expected to impact the next-generation magnetic devices.