Anisotropic Upper Critical Field of Single Crystal RNi2B2C (R = Y, Lu)

Measurements of the anisotropic upper critical field curves have been extended for YNi 2B2C and LuNi2B2C (T c = 15.6 K and 16.1 K, respectively). Measurements of R(T, H) were taken along the crystallographic directions of <100> and <110>. The resulting critical fields show an upward curvature near T c and a linear behavior at low temperature, which continues to below 2 K with little, if any, sign of saturation.

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Transport Properties and Upper Critical Field of Single Crystal Non-Magnetic LuxY1-xNi2B2C and Magnetic LuxGd1-xNi2B2C

International Journal of Modern Physics B ◽

10.1142/s0217979203021265 ◽

2003 ◽

Vol 17 (18n20) ◽

pp. 3493-3495 ◽

Cited By ~ 3

Author(s):

K. D. D. Rathnayaka ◽

D. G. Naugle ◽

A. C. Dumar ◽

M. P. Anatska ◽

P. C. Canfield

Keyword(s):

Magnetic Field ◽

Thermal Conductivity ◽

Low Temperature ◽

Single Crystal ◽

Critical Field ◽

Magnetic Impurity ◽

Positive Curvature ◽

Upper Critical Field ◽

Magnetic Impurities ◽

The Magnetic Field

The in-plane resistance of single crystal non-magnetic Lu x Y 1-x Ni 2 B 2 C and magnetic Lu x Gd 1-x Ni 2 B 2 C samples as a function of the magnitude and direction of the magnetic field and temperature have been measured. The superconducting upper critical field Hc2(T) is anisotropic for both. A positive curvature in Hc2(T) near Tc(x) is clearly observed only for the non-magnetic impurity. At low temperature Hc2(T) for the sample with magnetic impurities is strongly reduced. Thermopower, thermal conductivity and resistivity as a function of temperature are also reported for Lu x Gd 1-x Ni 2 B 2 C .

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The effect of epitaxy on the upper critical fields of evaporated niobium films

Journal of Materials Research ◽

10.1557/jmr.1989.0283 ◽

1989 ◽

Vol 4 (2) ◽

pp. 283-287 ◽

Cited By ~ 2

Author(s):

Gin-ichiro Oya ◽

Tetsuro Komukai ◽

Yasuji Sawada

Keyword(s):

Single Crystal ◽

Critical Field ◽

Surface Effect ◽

Upper Critical Field ◽

Critical Fields ◽

Surface Nucleation ◽

Single Crystal Films ◽

Crystal Films ◽

Upper Critical Fields ◽

Niobium Suboxide

Two upper critical fields normal (Bc2⊥) and parallel (Bc2∥) to the surfaces of both single-crystal and polycrystalline Nb films are studied at 4.2 K in relation to the purity and morphology of the films, in order to make properties of the single-crystal films clear. High-quality single-crystal Nb films (with transition temperature Tc of ∼9.3 K and normal resistivity ρn of ∼0.2 μΩ · cm) are found to have magnetic properties characterized by Bc2⊥ of 0.31 T as low as Bc2 (bulk upper critical field) of bulk Nb, and Bc2∥/Bc2⊥ of ∼1.85 as high as Bc3/Bc2 (where Bc3 is the surface nucleation critical field) of pure Nb. These properties depend strongly on high purity and surface smoothness of the films, which is naturally accompanied by superconductivity. Polycrystalline Nb films have higher Bc2⊥ and lower Bc2∥/Bc2⊥, which result from a decrease in purity of the films and a presence of normal-conducting niobium-suboxide layers at the surfaces of the films, and thereby a decrease of the surface effect in the films.

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CRITICAL FIELD AND MAGNETORESISTANCE OF SINGLE CRYSTAL TmNi2B2C

International Journal of Modern Physics B ◽

10.1142/s021797929900374x ◽

1999 ◽

Vol 13 (29n31) ◽

pp. 3715-3717 ◽

Cited By ~ 7

Author(s):

D. G. NAUGLE ◽

K. D. D. RATHNAYAKA ◽

K. CLARK ◽

P. C. CANFIELD

Keyword(s):

Magnetic Field ◽

Transition Temperature ◽

Single Crystal ◽

Critical Field ◽

Superconducting Transition Temperature ◽

Magnetic Transition ◽

Upper Critical Field ◽

Superconducting Transition ◽

Large Anisotropy ◽

The Magnetic Field

In-plane resistance as a function of magnitude and direction of the magnetic field and the temperature has been measured for TmNi2B2C from above the superconducting transition temperature at 10.7 K to below the magnetic transition TN=1.5 K. The superconducting upper critical field HC2(T) exhibits a large anisotropy and structure in the vicinity of TN. The magnetoresistance above TC is large and changes sign as the direction of the magnetic field is rotated from in-plane to parallel with the c-axis.

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UPPER CRITICAL FIELD OF UNCONVENTIONAL SUPERCONDUCTORS FROM CHEMICAL EQUILIBRIUM

International Journal of Modern Physics B ◽

10.1142/s0217979299003180 ◽

1999 ◽

Vol 13 (29n31) ◽

pp. 3443-3448 ◽

Cited By ~ 2

Author(s):

A. KALLIO ◽

J. HISSA ◽

T. HÄYRYNEN ◽

V. BRÄYSY

Keyword(s):

Magnetic Field ◽

Critical Field ◽

Normal State ◽

Chemical Equilibrium ◽

Critical Density ◽

Upper Critical Field ◽

Universal Function ◽

Zero Magnetic Field ◽

Mathematical Treatment ◽

Critical Fields

We have shown previously that many normal state properties of high Tc superconductors in zero magnetic field can be understood in terms of a single universal function f(t) in the scaled variable t=T/T*, where T* is connected with temperature independent gap 2Δ=2kBT*, which gives the binding energy of a pair in analogy with dissociation of molecules. The function f(t) determines the fraction of bosons (B++) and fermions (h+) at temperature T and it is obtained from the mathematical treatment of chemical equilibrium with respect to the reaction B++⇌ 2h+. Since for magnetic fields of reasonable strength the Zeeman energy is much smaller than the pseudo gap Δ~100K-800K, the function f(t) in the normal state is largely independent of magnetic field. The main effect of the magnetic field is to increase the tendency for bosons to localize. This means that the critical density nL for delocalization in the ab-plane direction and the critical density for superfluidity nc (≳ nL) both increase with magnetic field. This causes the corresponding temperatures TBL(H) and Tc(H) to go down with the field. Assuming a power law dependence nc(H)/nc(0)=1+AHμ, the upper critical fields for several heavy fermion compounds are shown to fall into a single curve. The purpose here is to show that the upper critical field Hc2(y) (y=Tc(H)/Tc(0)) can be expressed in a simple way in terms of f(t). We show that this theory predicts all the shapes of Hc2(y) observed in several unconventinal superconductors such as Tl 2 Ba 2 CuO 6+δ, with Tc=15 K.

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Single Crystal Growth and Anisotropy of the Upper Critical Field of CeIr3

Proceedings of J-Physics 2019: International Conference on Multipole Physics and Related Phenomena ◽

10.7566/jpscp.29.011007 ◽

2020 ◽

Author(s):

Yoshiki J. Sato ◽

Yusei Shimizu ◽

Fuminori Honda ◽

Ai Nakamura ◽

Yoshiya Homma ◽

...

Keyword(s):

Crystal Growth ◽

Single Crystal ◽

Critical Field ◽

Upper Critical Field ◽

Single Crystal Growth

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Mean-field analysis on the magnetic properties of non-centrosymmetric superconductor LaNiC2

Canadian Journal of Physics ◽

10.1139/cjp-2017-0178 ◽

2018 ◽

Vol 96 (2) ◽

pp. 189-193

Author(s):

Jia-Li Zhang

Keyword(s):

Critical Field ◽

Landau Theory ◽

Theoretical Calculations ◽

Mean Field ◽

Upper Critical Field ◽

Field Analysis ◽

S Wave ◽

Wave State ◽

Ginzburg Landau ◽

Upward Curvature

Based on two-band isotropic Ginzburg–Landau theory, we study the temperature dependence of upper critical field and London penetration depth for non-centrosymmetric superconductor LaNiC2. All the theoretical calculations fit the experimental data very well, especially the upward curvature of upper critical field near the critical temperature. Our results thus indicate that the two-gap scenario is better to account for the superconductivity of LaNiC2, and the Cooper pairs of this superconductor are in the conventional s-wave state.

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