Cooperative versus superparamagnetic behavior of dense magnetic nanoparticles in Co[sub 80]Fe[sub 20]/Al[sub 2]O[sub 3] multilayers

Sahoo, S.; Petracic, O.; Kleemann, W.; Stappert, S.; Dumpich, G.; Nordblad, P.; Cardoso, S.; Freitas, P. P.
June 2003
Applied Physics Letters;6/9/2003, Vol. 82 Issue 23, p4116
Academic Journal
Spin glasslike cooperative freezing is evidenced at low temperatures in a magnetic nanoparticle system prepared as a discontinuous metal-insulator multilayer [Co[SUB80]Fe[SUB20](0.9 nm)/Al[SUB2]O[SUB3](3 nm)][SUB10]. The relaxational behavior clearly deviates from Arrhenius-Néel--Brown-type and rather hints at collective freezing into a spin glass phase below T[SUBg] ≃ 61 K. Holelike memory imprinting during a stop-and-wait magnetization procedure corroborates the collective nature of the frozen state. Consequences for future magnetic terabit storage devices are briefly discussed.


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