Oliver Portmann

An inverse transition of magnetic domain patterns in ultrathin films

Inverse freezing and inverse melting are processes where a more symmetric phase is found at lower temperatures than at higher temperatures. Such inverse transitions are very rare. Here we report the existence of an inverse transition effect in ultrathin Fe films that are magnetized perpendicular to the film plane. The magnetization of these films is not uniform, but instead manifests itself as stripe domains with opposite perpendicular magnetization. Predictions relating to the disordering of this striped ground state in the limit of monolayer film thicknesses are controversial. Mean-field arguments predict a continuous reduction of the stripe width when the temperature is increased; other studies suggest that topological defects, such as dislocations and disclinations, might penetrate the system and induce geometrical phase transitions. We find, from scanning electron microscopy imaging, that when the temperature is increased, the low-temperature stripe domain structure transforms into a more symmetric, labyrinthine structure. However, at even higher temperatures and before the loss of magnetic order, a re-occurrence of the less symmetric stripe phase is found. Despite the widespread theoretical and experimental work on striped systems, this phase sequence and the microscopic instabilities driving it have not been observed before.

Scaling hypothesis for modulated systems

We propose a scaling hypothesis for pattern-forming systems in which modulation of the order parameter results from the competition between a short-ranged interaction and a long-ranged interaction decaying with some power

Stripe-domain nucleation and creep in ultrathin Fe films on Cu(1?0?0) imaged at the micrometre scale

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Temperature-Induced Domain Shrinking in Ising Ferromagnets Frustrated by a Long-Range Interaction

of the inverse distance. With

Scaling in Modulated Systems

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Experimental phase diagram of perpendicularly magnetized ultrathin ferromagnetic films.

being a spatial length characterizing the modulated phase, all thermodynamic quantities are predicted to scale like some power of

Stripe width and nonlocal domain walls in the two-dimensional dipolar frustrated Ising ferromagnet

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Observation of Stripe Mobility in a Dipolar Frustrated Ferromagnet

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Micromagnetism in the ultrathin limit

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Domain configuration in perpendicularly magnetized atomically thin iron particles

. The scaling dimensions