Imaging and control of ferromagnetism in LaMnO3/SrTiO3 heterostructures

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Science  14 Aug 2015:
Vol. 349, Issue 6249, pp. 716-719
DOI: 10.1126/science.aaa5198

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Control of magnetism in heterostructures

The interface between two different materials in a heterostructure can exhibit properties unique to either of the two materials alone. A well-known example is a conducting gas that forms when LaAlO3 is grown on SrTiO3, but only if the LaAlO3 layer is at least four unit cells thick. Wang et al. report a similarly abrupt magnetic transition in a heterostructure formed by another oxide (LaMnO3) on the same SrTiO3 substrate. Even though bulk LaMnO3 is an antiferromagnet, when six or more unit-cell layers of it were deposited on SrTiO3, it behaved like a ferromagnet.

Science, this issue p. 716


Oxide heterostructures often exhibit unusual physical properties that are absent in the constituent bulk materials. Here, we report an atomically sharp transition to a ferromagnetic phase when polar antiferromagnetic LaMnO3 (001) films are grown on SrTiO3 substrates. For a thickness of six unit cells or more, the LaMnO3 film abruptly becomes ferromagnetic over its entire area, which is visualized by scanning superconducting quantum interference device microscopy. The transition is explained in terms of electronic reconstruction originating from the polar nature of the LaMnO3 (001) films. Our results demonstrate that functionalities can be engineered in oxide films that are only a few atomic layers thick.

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