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arXiv · 1610.00783

Multiferroic magnetic spirals induced by random magnetic exchanges

Andrea Scaramucci·Hiroshi Shinaoka·Maxim V. Mostovoy·Markus Müller·Christopher Mudry·Matthias Troyer·Nicola A. Spaldin
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Abstract

Multiferroism can originate from the breaking of inversion symmetry caused by magnetic-spiral order. The usual mechanism for stabilizing a magnetic spiral is competition between magnetic exchange interactions differing by their range and sign, such as nearest-neighbor and next-nearest- neighbor interactions. Since the latter are usually weak the onset temperatures for multiferroism via this mechanism are typically low. By considering a realistic model for YBaCuFeO$_5$ we propose an alternative mechanism for magnetic-spiral order, and hence for multiferroism, that occurs at much higher temperatures. We show using Monte-Carlo simulations and electronic structure calculations based on density functional theory that the Heisenberg model on a geometrically non-frustrated lattice with only nearest-neighbor interactions can have a spiral phase up to high temperature when frustrating bonds are introduced randomly along a single crystallographic direction as caused, e.g., by a particular type of chemical disorder. This long-range correlated pattern of frustration avoids ferroelectrically inactive spin glass order. Finally, we provide an intuitive explanation for this mechanism and discuss its generalization to other materials.

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Andrea Scaramucci, Hiroshi Shinaoka, Maxim V. Mostovoy, Markus Müller, Christopher Mudry, Matthias Troyer, Nicola A. Spaldin. 2016-11-14. Multiferroic magnetic spirals induced by random magnetic exchanges. https://doi.org/10.1103/physrevx.8.011005

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