This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Researchers from the National University of Singapore (NUS), in collaboration with scientists from institutions in Switzerland, the Czech Republic and Germany, have demonstrated a way to introduce magnetism into an otherwise nonmagnetic two-dimensional (2D) semiconductor and subsequently control its magnetic properties using an electrical voltage. The findings, published in Science Advances, establish a new platform for investigating electrically controllable magnetism in atomically thin materials, with potential implications for future spintronic technologies.
The study, led by assistant professor Ahmet Avsar from the Department of Materials Science and Engineering at NUS, with Ph.D. student Qi Zhang as the first author, demonstrates how magnetism can be introduced into an air-stable 2D semiconductor and subsequently controlled through electrical gating. Conventional electronics use the charge of electrons to process and store information, while spintronics seeks to exploit an additional property: the electron's spin. Combining these two functionalities could enable new approaches to information processing and memory.
However, materials that exhibit robust magnetic order often lack the electrical tunability of semiconductors, while conventional semiconductors are generally nonmagnetic. Two-dimensional materials offer a promising route to overcome this limitation because their electronic properties can be strongly modified by applying an external gate voltage and tuning their thicknesses. The challenge is to introduce magnetic order without compromising their semiconductor functionality or environmental stability.
The researchers focused on platinum diselenide (PtSe2), an air-stable layered material whose electronic properties change dramatically with thickness. While bulk PtSe2 is metallic, reducing its thickness below approximately six atomic layers transforms it into a semiconductor. In its pristine form, PtSe2 is a nonmagnetic material.
By introducing a small concentration of iron (Fe) atoms into the PtSe2 crystal, the team induced magnetic order while retaining the material's thickness-dependent electronic properties. Atomic-resolution electron microscopy confirmed that Fe atoms substitute directly into the crystal lattice, without detectable clustering or phase segregation. Interestingly, the nature of the induced magnetism changes as the material becomes thinner.
Bulk Fe-doped PtSe2 exhibits ferromagnetism, in which magnetic moments tend to align in the same direction, with a Curie temperature of approximately 320 K, which is slightly above room temperature. Ferromagnetic signatures persist in metallic devices down to seven layers, although at substantially lower temperatures. In contrast, the thinner devices exhibit magnetotransport signatures consistent with antiferromagnetic order, in which neighboring magnetic moments favor opposing orientations.
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