Signature of room-temperature two-dimensional ferromagnetism in Ta0.67 V0.33 Se2

The discovery of ferromagnetism in van der Waals materials attracts intense research interest and holds profound implications for two-dimensional spintronic devices. However, in most cases the Curie temperature of van der Waals ferromagnets is much lower than room temperature, hindering their potential for device applications. In this study we report the discovery of room-temperature ferromagnetism in layered Ta0.67V0.33Se2. The single crystal is synthesized through the partial replacement of tantalum with vanadium. The crystal structure of Ta0.67V0.33Se2 closely resembles that of both 1T-VSe2 and 1T-TaSe2. The resultant Ta0.67V0.33Se2 exhibits a Hall sign reversal at around 60K, with the dominant carrier changing from electron type at higher temperatures to hole type at lower temperatures. The anomalous peak is observed in the longitudinal resistivity near the critical temperature, which is ascribed to the temperature-induced Lifshitz transition. Despite the fact that bulk 1T-VSe2 and 1T-TaSe2 are paramagnetic, Ta0.67V0.33Se2 displays room-temperature ferromagnetism, as evidenced by the hysteresis behavior observed in the field-dependent magnetization. Collective anomalies are observed at about 60K in both magnetization and transport measurements, indicating a strong correlation between electric and magnetic degrees of freedom. Moreover, room-temperature ferromagnetism is confirmed in few-layer Ta0.67V0.33Se2 through magneto-optic Kerr measurements. Our work provides a strategy for accessing two-dimensional high-Curie-temperature magnets, which hold promise for potential applications in spintronic devices.