Direct observation of competition between charge order and itinerant ferromagnetism in vdW crystal Fe5-xGeTe2

Abstract The interplay of symmetry-breaking ordered states, such as superconductivity, charge density waves (CDW), magnetism and pseudogap, is a fundamental issue in correlated system. CDW and antiferromagnetism often coexist in the proximity of phase diagram region in cuprates. It is also worthy nothing that different order states appear in a situation on comparable temperature scales, so these orders are intertwined and competing on the same footing. The magnetism of vdW material Fe5-xGeTe2 with the one of the highest reported bulk Curie temperatures, is found to be sensitive to thermal history and external magnetic field. However, the temperature-dependent magnetization with two characteristic points still lacks a unified picture to describe. Using angle-resolved photoemission spectroscopy, scanning tunneling microscopy, magnetic properties measurements, and the first-principles calculations, the complex yet intriguing magnetic behaviors are gradually unveiled. A competition mechanism between charge order and ferromagnetism is proposed and firmly observed by experimental measurements. As the ferromagnetic order strengthens at low temperature, the charge order will be suppressed. Exchange splitting in itinerant ferromagnetism plays a significant role in the temperature evolution of band structure and causes a Lifshitz transition, which provides more control means to realize novel devices at room temperature.