Laser-induced magnetization dynamics of lanthanide-doped permalloy thin films

• Published in: Physical review letters Vol. 102; no. 11; p. 117201
• Main Authors: Radu, I, Woltersdorf, G, Kiessling, M, Melnikov, A, Bovensiepen, U, Thiele, J-U, Back, C H
• Format: Journal Article
• Language: English
• Published: United States 20-03-2009
• ISSN: 0031-9007; 1079-7114
• DOI: 10.1103/PhysRevLett.102.117201

We investigate the effect of Ho, Dy, Tb, and Gd impurities on the femtosecond laser-induced magnetization dynamics of thin Permalloy films using the time-resolved magneto-optical Kerr effect. Varying the amount of Ho, Dy, Tb content from 0% to 8%, we observe a gradual change of the characteristic demagnetization time constant from approximately 60 to approximately 150 fs. In contrast, Gd concentrations up to 15% do not influence the time scale of the initial photoinduced magnetization loss. We propose a demagnetization mechanism that relies on strong magnetic inertia of the rare-earth dopant which stabilizes the ferrimagnetic ordering and thereby delays the demagnetization.