Martin, C., Gordon, R. T., Tanatar, M. A., Vannette, M. D., Tillman, M. E., Mun, E. D., ...
In- and out-of- plane magnetic penetration depth was studied in single crystals of NdFeAsO$_{0.9}$F$_{0.1}$. The low temperature behavior of the in-plane London penetration depth, $\lambda_{ab} (T)$,...
Magnetic field of Josephson vortices outside superconductors (2008)
Kogan, V. G., Dobrovitski, V. V.
We consider the structure of Josephson vortices approaching the junction boundary with vacuum in large area Josephson junctions with the Josephson length $\lambda_J$ large relative to the London...
Josephson junctions in narrow thin-film strips (2008)
Moshe, Maayan, Kogan, V. G., Mints, R. G.
We study the field dependence of the maximum supercurrent in narrow edge-type thin-film Josephson junctions. It is assumed that the junction extends across thin-film strip of width W that is much...
Superfluid density in gapless superconductor CeCoIn5 (2007)
Kogan, V. G., Prozorov, R., Petrovic, C.
Temperature dependence of the London penetration depth $\lambda$ measured in single crystals of CeCoIn$_5$ is interpreted as caused by a strong pair-breaking scattering that makes the...
Radio-frequency magnetic response of vortex lattices undergoing structural transformations (2007)
Prozorov, R., Kogan, V. G., Vannette, M D., Bud'ko, S. L., Canfield, P. C.
We report a clear anomaly in the rf response of a tunnel-diode resonator measured in borocarbide crystals in dc fields along the $c-$axis. We associate the anomaly in the dynamic magnetic...
The precondition for the BKT transition in thin superconducting films, the logarithmic intervortex interaction, is satisfied at distances short relative to $\Lambda=2\lambda^2/d$, $\lambda$ is the...
Li, J., Vaknin, D., Bud'ko, S. L., Canfield, P. C., Pal, D., Eskildsen, M. R., ...
X-ray diffraction studies of fine polycrystalline samples of MgB$_2$ in the superconducting state reveal that crystals orient with their \emph{c}-axis in a plane normal to the direction of the...
Kogan, V. G., Prozorov, R., Bud'ko, S. L., Canfield, P. C., Thompson, J. R., Karpinski, J., ...
The field dependence of the vortex core size $\xi(B)$ is incorporated in the London model, in order to describe reversible magnetization $M(B,T)$ for a number of materials with large Ginzburg-Landau...
Measuring the Penetration Depth Anisotropy in MgB$_2$ using Small-Angle Neutron Scattering (2005)
Pal, D., DeBeer-Schmitt, L., Bera, T., Cubitt, R., Dewhurst, C. D., Jun, J., ...
Using small-angle neutron scattering we have measured the misalignment between an applied field of 4 kOe and the flux-line lattice in MgB$_2$, as the field is rotated away from the c axis by an angle...
Tafuri, F., Kirtley, J. R., Born, D., Stornaiuolo, D., Medaglia, P. G., Orgiani, P., ...
We have made current-voltage (IV) measurements of artificially layered high-$T_c$ thin-film bridges. Scanning SQUID microscopy of these films provides values for the Pearl lengths $\Lambda$ that...
On the field dependence of the vortex core size (2004)
Kogan, V. G., Zhelezina, N. V.
We argue that in clean high-$\kappa$ type II superconductors, the low temperature vortex core size (defined as the coherence length $\xi$) in high fields should decrease with increasing applied field...
Anomalous Paramagnetic Effects in the Mixed State of LuNi2B2C (2004)
Park, Tuson, Sun, Y., Salamon, M. B., Malinowski, A. T., Hundley, M. F., Choi, Eun Mi, ...
Anomalous paramagnetic effects in dc magnetization were observed in the mixed state of LuNi2B2C, unlike any reported previously. It appears as a kink-like feature for H > 30 kOe and becomes more...
Penetration depth anisotropy in two-band superconductors (2003)
Kogan, V. G., Zhelezina, N. V.
The anisotropy of the London penetration depth is evaluated for two-band superconductors with arbitrary inter- and intra-band scattering times. If one of the bands is clean and the other is dirty in...
Properties of mesoscopic superconducting thin-film rings. London approach (2003)
Kogan, V. G., Clem, John R., Mints, R. G.
Superconducting thin-film rings smaller than the film penetration depth (the Pearl length) are considered. The current distribution, magnetic moment, and thermodynamic potential ${\cal F}(H,N,v)$ for...
Meissner response of anisotropic superconductors (2003)
The response field of a half-space anisotropic superconductor is evaluated for an arbitrary weak external field source. Example sources of a point magnetic moment and a circular current are...
Fluxoid dynamics in superconducting thin film rings (2003)
Kirtley, J. R., Tsuei, C. C., Kogan, V. G., Clem, J. R., Raffy, H., Li, Z. Z.
We have measured the dynamics of individual magnetic fluxoids entering and leaving photolithographically patterned thin film rings of the underdoped high-temperature superconductor...
Anisotropy parameters of superconducting MgB$_2$ (2002)
Data on macroscopic superconducting anisotropy of MgB$_2$ are reviewed. The data are described within a weak coupling two-gaps anisotropic s-wave model of superconductivity. The calculated ratio of...
Current in narrow channels of anisotropic superconductors (2002)
Kogan, V. G., Pokrovsky, V. L.
We argue that in channels cut out of anisotropic single crystal superconductors and narrow on the scale of London penetration depth, the persistent current must cause the transverse phase difference...
Free energy and torque for superconductors with different anisotropies of H_{c2} and lambda (2002)
The free energy is evaluated for a uniaxial superconductor with the anisotropy of the upper critical field, gamma_H = H_{c2,ab}/H_{c2,c}, different from the anisotropy of the penetration depth...
Miranovic, P., Machida, K., Kogan, V. G.
The upper critical field Hc2 is evaluated for weakly-coupled two-band superconductors. By modeling the actual bands and the gap distribution of MgB2 by two Fermi surface spheroids with average...
Effects of La substitution on superconducting state of CeCoIn5 (2002)
Petrovic, C., Bud'ko, S. L., Kogan, V. G., Canfield, P. C.
We report effects of La substitution on superconducting state of heavy fermion superconductor CeCoIn5, as seen in transport and magnetization measurements. As opposed to the case of conventional...
Macroscopic anisotropy in superconductors with anisotropic gaps (2002)
It is shown within the weak-coupling model that the macroscopic superconducting anisotropy for materials with the gap varying on the Fermi surface cannot be characterized by a single number, unlike...
Bud'ko, S. L., Kogan, V. G., Canfield, P. C.
The recently discovered intermetallic superconductor MgB2 appears to have a highly anisotopic upper critical field with Hc2(max)/Hc2(min} = \gamma > 5. In order to determine the temperature...
Effect of fluctuations on vortex lattice structural transitions in superconductors (2001)
The rhombic-to-square transition field $H_{\Box}(T)$ for cubic and tetragonal materials in fields along [001] is evaluated using the nonlocal London theory with account of thermal vortex...
Elastic moduli of vortex lattices within nonlocal London model (2001)
Vortex lattice (VL) elastic response is analyzed within nonlocal London model. The squash modulus turns zero at the field $H_{\Box}$ where VL undergoes square-to-rhombus structural transition. In the...
Anisotropy of superconducting MgB2 as seen in electron spin resonance and magnetization data (2001)
Simon, F., Janossy, A., Feher, T., Muranyi, F., Garaj, S., Forro, L., ...
We have observed the conduction electron spin resonance (CESR) in fine powders of MgB2 both in the superconducting and normal states. The Pauli susceptibility is chi_s=2.0*10^{-5} emu/mole in the...
Field evolution of vortex lattice in LuNi_2B_2C seen by decoration in fields up to 1.5 kOe (2001)
Vinnikov, L. Ya., Barkov, T. L., Canfield, P. C., Bud'ko, S. L., Kogan, V. G.
Evolution of the vortex lattice, the rhombus-square transition included, for LuNi_2B_2C in the field along the c crystal axis, is tracked by the decoration technique pushed up to the record high (for...
Eskildsen, M. R., Abrahamsen, A. B., Kogan, V. G., Gammel, P. L., Mortensen, K., Andersen, N. H., ...
We have investigated the temperature dependence of the H || c flux line lattice structural phase transition from square to hexagonal symmetry, in the tetragonal superconductor LuNi_2B_2C (T_c = 16.6...
Direct measurement of single fluxoid dynamics in superconducting rings (2001)
Kirtley, J. R., Tsuei, C. C., Raffy, H., Li, Z. Z., Kogan, V. G., Clem, J. R., ...
We have measured the dynamics of individual magnetic fluxoids entering and leaving thin film, photolithographically patterned rings of underdoped high-temperature superconductor BSCCO using a...
Nature of 45 degree vortex lattice reorientation in tetragonal superconductors (2000)
Knigavko, A., Kogan, V. G., Rosenstein, B.
The transformation of the vortex lattice in a tetragonal superconductor which consists of its 45 degree reorientation relative to the crystal axes is studied using the nonlocal London model. It is...
Magnetic field of an in-plane vortex outside a layered superconductor (1998)
Kirtley, J. R., Kogan, V. G., Clem, J. R., Moler, K. A.
We present the solution to London's equations for the magnetic fields of a vortex oriented parallel to the plane, and normal to a crystal face, of a layered superconductor. These expressions account...