Direct observation of the energy gain underpinning ferromagnetic superexchange in the electronic structure of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>CrGeTe</mml:mi><mml:mn>3</mml:mn></mml:msub></mml:math>
Matthew D. Watson, Igor Marković, Federico Mazzola, Akhil Rajan, Edgar Abarca Morales, David M. Burn, T. Hesjedal, G. van der Laan, Saumya Mukherjee, T. K. Kim, Chiara Bigi, I. Vobornik, Monica Ciomaga Hatnean, G. Balakrishnan, P. D. C. King
Abstract
We investigate the temperature-dependent electronic structure of the van der Waals ferromagnet, ${\mathrm{CrGeTe}}_{3}$. Using angle-resolved photoemission spectroscopy, we identify atomic- and orbital-specific band shifts upon cooling through ${T}_{\mathrm{C}}$. From these, together with x-ray absorption spectroscopy and x-ray magnetic circular dichroism measurements, we identify the states created by a covalent bond between the Te $5p$ and the Cr ${e}_{g}$ orbitals as the primary driver of the ferromagnetic ordering in this system, while it is the Cr ${t}_{2g}$ states that carry the majority of the spin moment. The ${t}_{2g}$ states furthermore exhibit a marked bandwidth increase and a remarkable lifetime enhancement upon entering the ordered phase, pointing to a delicate interplay between localized and itinerant states in this family of layered ferromagnets.