On May 20, 2024, at the invitation of Professor Tang Chun from the School of Civil Engineering and Mechanics, Chair Professor Wang Jiantao from the Institute of Physics, Chinese Academy of Sciences, visited our university for academic exchange and delivered a guest lecture titled "Structural Phase Transition and Magnetic Phase Transition of MnCoGe Compounds" in conference room 414 of Leisi Building. The lecture was presided over by Tang Chun, with faculty members Li Wenlong, Wang Liya, Wang Ruijie, Xia Jun, and students from the school attending.

During the lecture, Professor Wang Jiantao gave a detailed introduction into the phenomena of the magnetically induced phase transition and the magnetocaloric effect in MnCoGe-based alloys, shedding light on the theoretical understanding behind such structural phase transitions, hysteresis behavior, and the magnetocaloric effect caused by Co vacancies in MnCoGe-based alloys. He discussed in-depth the structural phase transitions behavior of MnCo1−xGe alloys in terms of the coupling distance of magnetic atoms, symmetry, and the magneto-volume effect. This research has recently ignited a surge of interest among international scholars in the field of magnetocaloric effect and holds significant prospects for applications in magnetic cooling technology. Subsequently, Professor Wang explained the controllable design of the magnetocaloric effect in ferromagnetic materials to achieve thermally induced structural phase transitions and significant room temperature magnetothermal effects through methods such as element substitution, interstitial atom doping, and element vacancies. He provided in-depth analysis of the underlying mechanisms into each approach. He also showcased the concurrent progress in achieving near-zero expansion by controlling the expansion coefficient through the use of magneto-volume effect during the antiferromagnetic to paramagnetic phase transition, which allows emergence of negative thermal expansion in the functional material.

        Professor Wang’s profound knowledge and rigorous scientific attitude left a deep impression on the attending faculty and students. After the lecture, extensive discussions ensued on issues such as the temperature sensitivity of modulus when making nano-indentations on the SiO2 surface of ceramics, the mechanism of structure transformation during phase transitions, and the energy state and judging criteria for ferromagnetic and antiferromagnetic configurations in magnetic systems. Professor Wang Jiantao gave thorough responses to the questions, and offered strategies for solving the the problems.

        This lecture presented a rich and insightful discussion into magnetically controlled structural phase transition material design, sparked heated discussions, and highlighted the importance of fundamental and theoretical research in guiding practical applications.