3 research outputs found
Ruthenocuprates RuSr2(Eu,Ce)2Cu2O10: Intrinsic magnetic multilayers
We report ac susceptibility data on RuSr_2(Eu,Ce)_2Cu_2O_(10-y) (Ru-1222, Ce
content x=0.5 and 1.0), RuSr_2GdCu_2O_8 (Ru-1212) and SrRuO_3. Both Ru-1222
(x=0.5, 1.0) sample types exhibit unexpected magnetic dynamics in low magnetic
fields: logarithmic time relaxation, switching behavior, and `inverted'
hysteresis loops. Neither Ru-1212 nor SrRuO_3 exhibit such magnetic dynamics.
The results are interpreted as evidence of the complex magnetic order in
Ru-1222. We propose a specific multilayer model to explain the data, and note
that superconductivity in the ruthenocuprate is compatible with both the
presence and absence of the magnetic dynamics.Comment: 9 pages, 11 figures, Revtex; submitted to Phys.Rev.
Magnetic relaxation and dipole-coupling-induced magnetization in nanostructured thin films during growth: A cluster Monte Carlo study
For growing inhomogeneous thin films with an island nanostructure similar as
observed in experiment, we determine the nonequilibrium and equilibrium
remanent magnetization. The single-island magnetic anisotropy, the dipole
coupling, and the exchange interaction between magnetic islands are taken into
account within a micromagnetic model. A cluster Monte Carlo method is developed
which includes coherent magnetization changes of connected islands. This causes
a fast relaxation towards equilibrium for irregularly connected systems. We
analyse the transition from dipole coupled islands at low coverages to a
strongly connected ferromagnetic film at high coverages during film growth. For
coverages below the percolation threshold, the dipole interaction induces a
collective magnetic order with ordering temperatures of 1 - 10 K for the
assumed model parameters. Anisotropy causes blocking temperatures of 10 - 100 K
and thus pronounced nonequilibrium effects. The dipole coupling leads to a
somewhat slower magnetic relaxation.Comment: 13 pages, 6 figures, revised manuscrip