Amorphous magnetic semiconductors with Curie temperatures above room temperature

Recently, amorphous magnetic semiconductors as a new family of magnetic semiconductors have been developed by oxidizing ferromagnetic amorphous metals/alloys. Intriguingly, tuning the relative atomic ratios of Co and Fe in a Co-Fe-Ta-B-O system leads to the formation of an intrinsic magnetic semiconductor. Starting from high Curie-temperature amorphous ferromagnets, these amorphous magnetic semiconductors show Curie temperatures well above room temperature. Among them, one typical example is a p-type Co_28.6Fe_12.4Ta_4.3B_8.7O₄₆ magnetic semiconductor, which has an optical bandgap of ∼2.4 eV, room-temperature saturation magnetization of ∼433 emu/cm³, and the Curie temperature above 600 K. The amorphous Co_28.6Fe_12.4Ta_4.3B_8.7O₄₆ magnetic semiconductor can be integrated with n-type Si to form p–n heterojunctions with a threshold voltage of ∼1.6 V, validating its p-type semiconducting character. Furthermore, the demonstration of electric field control of its room-temperature ferromagnetism reflects the interplay between the electricity and ferromagnetism in this material. It is suggested that the carrier density, ferromagnetism and conduction type of an intrinsic magnetic semiconductor are controllable by means of an electric field effect. These findings may pave a new way to realize magnetic semiconductor-based spintronic devices that work at room temperature. (paper)