Cedomir Petrovic

Boron Isotope Effect in Superconducting MgB2

We report the preparation method of and boron isotope effect for MgB2, a new binary intermetallic superconductor with a remarkably high superconducting transition temperature T(c)(10B) = 40.2 K. Measurements of both temperature dependent magnetization and specific heat reveal a 1.0 K shift in T(c) between Mg11B2 and Mg10B2. Whereas such a high transition temperature might imply exotic coupling mechanisms, the boron isotope effect in MgB2 is consistent with the material being a phonon-mediated BCS superconductor.

Field-Induced Quantum Critical Point in C e C o I n 5

The resistivity of the heavy-fermion superconductor CeCoIn5 was measured as a function of temperature, down to 25 mK and in magnetic fields of up to 16 T applied perpendicular to the basal plane. With increasing field, we observe a suppression of the non-Fermi liquid behavior, rho approximately T, and the development of a Fermi liquid state, with its characteristic rho=rho(0)+AT2 dependence. The field dependence of the T2 coefficient shows critical behavior with an exponent of 1.37. This is evidence for a field-induced quantum critical point (QCP), occurring at a critical field which coincides, within experimental accuracy, with the superconducting critical field H(c2). We discuss the relation of this field-tuned QCP to a change in the magnetic state, seen as a change in magnetoresistance from positive to negative, at a crossover line that has a common border with the superconducting region below approximately 1 K.

Carbon doping of superconducting magnesium diboride

Abstract We present details of synthesis optimization and physical properties of nearly single phase carbon doped MgB 2 with a nominal stoichiometry of Mg(B 0.8 C 0.2 ) 2 synthesized from magnesium and boron carbide (B 4 C) as starting materials. The superconducting transition temperature is ≈22 K (≈17 K lower than in pure MgB 2 ). The temperature dependence of the upper critical field is steeper than in pure MgB 2 with H c2 (10 K )≈9 T. Temperature dependent specific heat data taken in different applied magnetic fields suggest that the two-gap nature of superconductivity is still preserved for carbon doped MgB 2 even with such a heavily suppressed transition temperature. In addition, the anisotropy ratio of the upper critical field for T / T c ≈2/3 is γ ≈2. This value is distinct from 1 (isotropic) and also distinct from 6 (the value found for pure MgB 2 ).

Anisotropy and large magnetoresistance in the narrow-gap semiconductor FeSb2

A study of the anisotropy in magnetic, transport, and magnetotransport properties of

Field-induced quantum critical point in CeCoIn5

{\mathrm{FeSb}}_{2}

Magnetism and superconductivity in Ce_2RhIn_8

has been made on large single crystals grown from Sb flux. Magnetic susceptibility of

Superconducting Vortices in CeCoIn5: Toward the Pauli-Limiting Field

{\mathrm{FeSb}}_{2}

Hexagonal and Square Flux Line Lattices in CeCoIn5

shows diamagnetic to paramagnetic crossover around 100 K. Electrical transport along two axes is semiconducting, whereas the third axis exhibits a metal-semiconductor crossover at temperature

Effects of La Substitution on the Superconducting State of CeCoIn5

{T}_{\mathrm{cr}}

Surface-induced Magnetic Fluctuations in a Single-Crystal NiBi3 Superconductor

which is sensitive to current alignment and ranges between 40 and 80 K. In