S. M. Ramos

Publications (4)17.29 Total impact

• Article: Large variations in the magnetic ordering behavior of EuCu(2)As(2) with the application of external pressure and magnetic field.

  K Sengupta, M Alzamora, M B Fontes, E V Sampathkumaran, S M Ramos, E N Hering, E M B Saitovitch, P L Paulose, R Ranganathan, Th Doert, J P F Jemetio
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  ABSTRACT: The influence of external pressure on the electrical transport and magnetic properties of EuCu(2)As(2), crystallizing in a ThCr(2)Si(2)-type structure, is reported. The system is known to be an antiferromagnet below T(N) ≈ 15 K in the absence of external magnetic fields. We find that there is a gradual reduction of T(N) with the application of a magnetic field with an extrapolated value of the critical field of around 18 kOe which can drive T(N) to zero. Electrical resistivity under pressure (<11 GPa) reveals that the magnetic ordering temperature is pushed up dramatically to higher temperatures which is quite interesting if compared with the behavior in isostructural FeAs-based systems containing Eu. Above 7 GPa, the pressure-induced state appears to be ferromagnetic. The results thus reveal interesting changes in the magnetic ordering behavior of this compound with increasing pressure and magnetic fields.
  Journal of Physics Condensed Matter 03/2012; 24(9):096004. · 2.55 Impact Factor
• Article: Superconducting quantum critical point in CeCoIn(5-x)Sn(x).

  S M Ramos, M B Fontes, E N Hering, M A Continentino, E Baggio-Saitovich, F Dinóla Neto, E M Bittar, P G Pagliuso, E D Bauer, J L Sarrao, J D Thompson
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  ABSTRACT: We report a combined pressure-doping study in the nearly two-dimensional heavy fermion superconductor CeCoIn5 as its superconducting phase is driven to the normal state by Sn doping and/or applied pressure. Temperature-pressure-dependent electrical resistivity measurements were performed at the vicinity of a superconducting quantum critical point where Tc→0. A universal plot of the concentration- and pressure-dependent phase diagram suggests that for the concentrations studied a single mechanism is responsible for reducing Tc and bringing the system to the superconducting quantum critical point. A two-band model with hybridization controlled by pressure and doping provides a consistent description of the phase diagram and the suppression of the d-wave superconductivity in this material.
  Physical Review Letters 09/2010; 105(12):126401. · 7.37 Impact Factor
• Source

  Available from: ArXiv

  Article: Kondo Effect and Spin Glass Behavior of Dilute Iron Clusters in Silver Studied by M\"{o}ssbauer Spectroscopy and Resistivity

  W. T. Herrera, S. M. Ramos, E. M. Baggio-Saitovitch, F. J. Litterst
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  ABSTRACT: Thin films of silver containing 0.3 - 1.5 at % Fe have been prepared by vapor co-deposition. Depending on substrate temperature and iron concentration we could systematically follow the formation of nanometer size clusters of iron from initially dilute iron monomers. samples were characterized via X-ray diffraction, resistivity and M\"{o}ssbauer spectroscopic measurements. The magnetic behavior derived from M\"{o}ssbauer data can be best described with an ensemble of ferromagnetic mono-domain particles. The magnetic freezing observed at low temperatures, is controlled via the inter-particle interactions mediated via conduction electron polarization, i.e. RKKY interaction. The interaction of the cluster magnetic moments with the conduction electron sea is best quantified by the electrical resistivity data. For all studied concentrations we find a non-monotonic variation with temperature which can be understood by competing shielding of the cluster moments by conduction electron spin scattering due to Kondo effect and the magnetic coupling.
  09/2008;
• Source

  Available from: Eduardo Novaes Hering

  Article: Tuning the pressure-induced superconducting phase in doped CeRhIn5.

  L Mendonça Ferreira, T Park, V Sidorov, M Nicklas, E M Bittar, R Lora-Serrano, E N Hering, S M Ramos, M B Fontes, E Baggio-Saitovich, Hanoh Lee, J L Sarrao, J D Thompson, P G Pagliuso
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  ABSTRACT: Pressure- and temperature-dependent heat capacity and electrical resistivity experiments on Sn- and La-doped CeRhIn5 are reported for two samples with specific concentrations, Ce(0.90)La(0.10)RhIn5 and CeRhIn(4.84)Sn(0.16), which present the same TN=2.8 K. The obtained P-T phase diagrams for doped CeRhIn5 compared to that for the pure compound show that Sn doping shifts the diagram to lower pressures while La doping does exactly the opposite, indicating that the important energy scale to define the pressure range for superconductivity in CeRhIn5 is the strength of the on-site Kondo coupling.
  Physical Review Letters 08/2008; 101(1):017005. · 7.37 Impact Factor