H. S. Jeevan

Interplay of antiferromagnetism, ferromagnetism, and superconductivity in EuFe2(As1-xPx)2 single crystals

We report a systematic study on the influence of antiferromagnetic and ferromagnetic phases of Eu^2+ moments on the superconducting phase upon doping the As site by isovalent P, which acts as chemical pressure on EuFe_2As_2. Bulk superconductivity with transition temperatures of 22 K and 28 K are observed for x=0.16 and 0.20 samples respectively. The Eu ions order antiferromagnetically for x =0.22 whereupon the Eu ions order ferromagnetically. Density functional theory based calculations reproduce the observed experimental findings consistently. We discuss in detail the coexistence of superconductivity and magnetism in a tiny region of the phase space and comment on the competition of ferromagnetism and superconductivity in the title compound.

Relevance of Ferromagnetic Correlations for the Electron Spin Resonance in Kondo Lattice Systems

Electron spin resonance (ESR) measurements of the ferromagnetic (FM) Kondo lattice system CeRuPO show a well defined ESR signal which is related to the Ce3+ magnetism. In contrast, no ESR could be observed in the antiferromagnetic (AFM) homologue CeOsPO. Additionally, we detect an ESR signal in ferromagnetic YbRh while it was absent in a number of Ce or Yb intermetallic compounds with dominant AFM exchange. Thus, the observation of an ESR signal in a Kondo lattice is neither specific to Yb nor to the proximity to a quantum critical point, but seems to be connected to the presence of FM fluctuations. These conclusions not only provide a basic concept to understand the ESR in Kondo lattice systems even well below the Kondo temperature (as observed in YbRh2Si2) but point out ESR as a prime method to investigate directly the spin dynamics of the Kondo ion.

Effects of magnetic ordering on dynamical conductivity: Optical investigations of EuFe2As2 single crystals

The magnetic, transport and optical properties of EuFe

Quasiquartet crystal-electric-field ground state with possible quadrupolar ordering in the tetragonal compound ybRu2Ge2

_2

Fully gapped superconductivity with no sign change in the prototypical heavy-fermion CeCu2Si2

As

Upper critical magnetic field of KxFe2−ySe2 and Eu0.5K0.5Fe2As2 single crystals

_2

Pressure Tuning of the Interplay of Magnetism and Superconductivity in CeCu2Si2

single crystals have been investigated parallel and perpendicular to the

Pressure-induced change of the pairing symmetry in superconducting CeCu2Si2

ab

Anisotropy, disorder, and superconductivity in CeCu2Si2 under high pressure

-plane. The anisotropy

Electron spin resonance in Eu-based iron pnictides

\rho_c/\rho_{ab}\approx 8