http://doi.org/10.1002/advs.202508148

A research team led by Professor Jung-Chun-Andrew Huang from the Department of Physics at National Cheng Kung University (NCKU), in collaboration with scientists at the National Synchrotron Radiation Research Center (NSRRC), has achieved a major breakthrough in uncovering the key mechanism behind room-temperature ferromagnetism in diluted magnetic semiconductors. This important discovery was officially accepted for publication by the prestigious journal Advanced Science two days ago, highlighting Taiwan’s leadership in materials physics and advanced spectroscopy.

The study focused on cobalt-doped zinc oxide (Co:ZnO) thin films. Using polarization-dependent hard X-ray photoemission spectroscopy (HAXPES), the team directly observed a donor band with “s-orbital character” crossing the Fermi level—a feature previously hypothesized but never experimentally confirmed. This metallic-like donor band, derived from Zn 4s electrons, couples with Co²⁺ magnetic moments to enable ferromagnetism at room temperature. The finding provides crucial evidence supporting the long-standing theoretical model of donor-impurity-band-driven magnetism and clarifies the role of native structural defects such as oxygen vacancies and zinc interstitials.

This work not only solves a long-standing mystery in oxide-based magnetic semiconductors but also lays a solid foundation for designing novel spintronic devices and two-dimensional magnetic semiconductors that operate at ambient conditions. The project was a joint effort involving National Chung Kung University, NSRRC, NPTU, and Japan’s SPring-8 synchrotron facility, and was funded by Taiwan’s National Science and Technology Council (NSTC 113-2124-M-006-001).

＊Professor Jung-Chun-Andrew Huang’s instruments for the Shared Instrument Service: https://cis-cfc.ncku.edu.tw/p/412-1209-31366.php?Lang=zh-tw