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AM: Magnetismus
AM 4: Nanokristalline Materialien
AM 4.2: Vortrag
Montag, 26. März 2001, 15:00–15:15, S 5.4
Magnetic hardening and spin-glass phenomena in nanocrystalline FeNbB at low temperatures — •Ivan Skorvanek1, Sven Skwirblies2, and Jürgen Kötzler2 — 1Institute of Experimental Physics, Slovak Academy of Sciences, Kosice — 2Institute of Applied Physics, Univ. Hamburg
Recent studies of magnetic behaviour in nanocrystalline Fe80.5Nb7B12.5 alloys revealed an unexpected increase of coercivity by nearly two orders of magnitude at temperatures below ∼50 K[1]. In this paper, the first studies of the frequency dependence of complex susceptibility χ(ω) versus measuring temperature have been performed by SQUID measurements down to 1.8 K. The presence of the glass transition is supported by the validity of a dynamic scaling (critical exponents β=0.7 ± 0.05 and z ν=10.5± 2). The observed results indicate the presence of collective magnetic dynamics and critical slowing down at a finite temperature Tg=6.1 K, which coincides well with the temperature where the most pronounced changes of coercivity takes place. As a common origin of these features we consider a small fluctuation of the exchange coupling between grains.
[1] I. Skorvanek, P. Duhaj, R. Grössinger, JMMM 215-216 (2000) 436