Jannis Maiwald from Meigan Aronson’s research group has been awarded € 2,000 by the University of Augsburg for best outstanding scientific dissertation.

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In his PhD research he investigated iron-based superconductors, specifically EuFe2As2, a “122” compound containing the magnetic rare earth element Europium. The research shows how the orientation of the internal crystal structure of the material can be changed at low temperatures upon application of a miniscule in-plane magnetic field, on the order of 0.1T, two orders of magnitude smaller than what is needed in other iron-based superconductors. The reorientation of structural domains is persistent upon removal of the field and even subsequent heating to 190 K.

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Therefore, this effect can be used to reveal the large in-plane anisotropy (the quality of having different properties in different dimensions) which is present in these types of materials, making the commonly-used application of external pressure obsolete. An investigation by a probe with neutrons revealed that a multistage magnetic de-twinning effect occurs at low temperatures in this compound, in which the internal crystal structure changes its orientation up to three times with increasing field.

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Jannis’ investigation is notable for its extraordinary range of activities and involvement of the three major approaches in solid state physics: theoretical, experimental and computational. Besides single crystal synthesis and characterization, the research included physical measurements to theoretical work and even numerical calculations. It produced evidence for the highly unexpected physical phenomenon of persistent multistage magnetic de-twinning in EuFe2As2 and presented a novel microscopic theory which quantitatively explains the phase diagram of this system.

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Jannis will be travelling to Germany to receive the award in person this May.

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Read the dissertation in full and view his most recent publication here.