Sina Zapf

EuFe2(As(1-x)P(x))2: reentrant spin glass and superconductivity.

By systematic investigations of the magnetic, transport, and thermodynamic properties of single crystals of EuFe(2)(As(1-x)P(x))(2) (0≤x≤1), we explore the complex interplay of superconductivity and Eu(2+) magnetism. Below 30 K, two magnetic transitions are observed for all P substituted crystals, suggesting a revision of the phase diagram. In addition to the canted A-type antiferromagnetic order of Eu(2+) at ∼20  K, a spin glass transition is discovered at lower temperatures. Most remarkably, the reentrant spin glass state of EuFe(2)(As(1-x)P(x))(2) coexists with superconductivity around x≈0.2.

Persistent Detwinning of Iron-Pnictide EuFe_{2}As_{2} Crystals by Small External Magnetic Fields.

S. Zapf, ∗ C. Stingl, K. W. Post, J. Maiwald, 4 N. Bach, I. Pietsch, D. Neubauer, A. Löhle, C. Clauss, S. Jiang, H. S. Jeevan, 5 D. N. Basov, P. Gegenwart, 4 and M. Dressel 1. Physikalisches Institut, Universität Stuttgart, Pfaffenwaldring 57, 70550 Stuttgart, Germany I. Physikalisches Institut, Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany Department of Physics, University of California, San Diego, La Jolla, California 92093, USA Experimentalphysik VI, Universität Augsburg, Universitätsstraße 1, 86135 Augsburg, Germany Department of Physics, PESITM, Sagar Road, 577204 Shimoga, India (Dated: August 29, 2014)

Europium-based iron pnictides: a unique laboratory for magnetism, superconductivity and structural effects

Despite decades of intense research, the origin of high-temperature superconductivity in cuprates and iron-based compounds is still a mystery. Magnetism and superconductivity are traditionally antagonistic phenomena; nevertheless, there is basically no doubt left that unconventional superconductivity is closely linked to magnetism. But this is not the whole story; recently, also structural effects related to the so-called nematic phase gained considerable attention. In order to obtain more information about this peculiar interplay, systematic material research is one of the most important attempts, revealing from time to time unexpected effects. Europium-based iron pnictides are the latest example of such a completely paradigmatic material, as they display not only spin-density-wave and superconducting ground states, but also local Eu2+ magnetism at a similar temperature scale. Here we review recent experimental progress in determining the complex phase diagrams of europium-based iron pnictides. The conclusions drawn from the observations reach far beyond these model systems. Thus, although europium-based iron pnictides are very peculiar, they provide a unique platform to study the common interplay of structural-nematic, magnetic and electronic effects in high-temperature superconductors.

Tracing the

Consecutive proton irradiation of iron pnictides reduces the superconducting transition temperature to decrease monotonically. Our systematic optical THz investigations of Ba(Fe

s_\pm

_{0.9}

-symmetry in iron pnictides by controlled disorder

Co

Boson peak in overdoped manganites La1−xCaxMnO3

_{0.1}

Electronic scattering effects in europium-based iron pnictides

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Reentrant phases in electron-doped

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\text{EuFe}_2\text{As}_2

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