Journal
JOURNAL OF PHYSICS-CONDENSED MATTER
Volume 27, Issue 20, Pages -Publisher
IOP PUBLISHING LTD
DOI: 10.1088/0953-8984/27/20/206003
Keywords
magnetism; first-principles; density functional theory
Categories
Funding
- US Department of Energy [DE-FG02-06ER46304]
- Office of Science of the US Department of Energy [DE-AC02-05CH11231]
- US Department of Energy (DOE) Office of Science [DE-AC52-06NA25396, DE-AC04-94AL85000]
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The exchange interaction among electrons is one of the most fundamental quantum mechanical interactions in nature and underlies any magnetic phenomena from ferromagnetic ordering to magnetic storage. The current technology is built upon a thermal or magnetic field, but a frontier is emerging to directly control magnetism using ultrashort laser pulses. However, little is known about the fate of the exchange interaction. Here we report unambiguously that photoexcitation is capable of quenching the exchange interaction in all three 3d ferromagnetic metals. The entire process starts with a small number of photoexcited electrons which build up a new and self-destructive potential that collapses the system into a new state with a reduced exchange splitting. The spin moment reduction follows a Bloch-like law as M-z(Delta E) = M-z(0)(1 - Delta E/Delta E-0)(1/beta), where Delta E is the absorbed photon energy and beta is a scaling exponent. A good agreement is found between the experimental and our theoretical results. Our findings may have a broader implication for dynamic electron correlation effects in laser-excited iron-based superconductors, iron borate, rare-earth orthoferrites, hematites and rare-earth transition metal alloys.
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