Evolution of the magnetic order of Fe and Eu sublattices in Eu1−xCaxFe2As2 (0 x 1) single crystals

• Published in: Journal of physics. Condensed matter 2018-10, Vol.30 (41)
• Main Authors: Harnagea, Luminita, Kumar, Rohit, Singh, Surjeet, Wurmehl, S, Wolter, Anja U B, Büchner, B
• Format: Article
• Language: English
• Subjects: antiferromagnetism; Ca-doped EuFe; Fe-based superconductors; phase diagram; spin-density-wave transition
• ISSN: 0953-8984; 1361-648X
• DOI: 10.1088/1361-648X/aadea6

Single crystals of Eu1−xCaxFe2As2 () are grown using the high-temperature solution-growth method employing FeAs self-flux. Structural and chemical analysis indicates that these crystals are homogeneous and their lattice parameters exhibit a gradual monotonic decrease with increasing Ca concentration. Detailed magnetic, specific heat and resistivity data were used to construct a phase diagram which depicts the evolution of the structural/spin-density-wave transition at T0, and of the antiferromagnetic (AFM) ordering temperature of the Eu moments at TN. We found out that while TN decreases monotonically from 19.1 K (for x  =  0) to below 2 K (for ), T0 remains almost constant up to x  =  xc and decreases steadily for higher values of x. Annealing at low temperatures for several days leads to enhancement of TN and T0 by a few kelvin and sharpened the anomalies associated with these transitions. However, annealing did not change the variation of TN and T0 across the series. The observation that T0 is almost constant until the long-range AFM ordering of the Eu2+ moments gets destroyed, suggests a subtle interrelationship between the Eu2+ and Fe2+ magnetic sublattices.