Pressure effects on the superconducting properties of YBa_2Cu_4O_8

Measurements of the magnetization under high hydrostatic pressure (up to 10.2 kbar) in YBa_2Cu_4O_8 were carried out. From the scaling analysis of the magnetization data the pressure induced shifts of the transition temperature T_c, the volume V and the anisotropy \gamma have been obtained. It was shown that the pressure induced relative shift of T_c mirrors essentially that of the anisotropy. This observation uncovers a novel generic property of anisotropic type II superconductors, that inexistent in the isotropic case.Comment: 4 pages, 3 figure

Broadening Our Perspective on Spirituality and Coping among Women with Breast Cancer and their Families: Implications for Practice

The purpose of this paper is to illustrate the role of spirituality in coping among women with breast cancer and their families. This phenomenological study was guided by family systems theory and the recognition that a family is a complex system whereby family members interact with one another as well as with the outside world. A change in any of these interactions/relationships can affect the rest of the system, and the diagnosis of breast cancer in mothers within the family system is no exception. Five families (five women, five men and six children) comprising a total of 16 participants took part in this study. The women in this study reported using a number of methods to cope with their illness, one of which was utilising their spiritual beliefs. Although they placed a great deal of importance upon their spiritual beliefs, their families did not. The implications of this reality upon nursing practice will be discussed here

Implications of the isotope effects on the magnetization, magnetic torque and susceptibility

We analyze the magnetization, magnetic torque and susceptibility data of La2-xSrxCu(16,18)O4 and YBa2(63,65)CuO7-x near Tc in terms of the universal 3D-XY scaling relations. It is shown that the isotope effect on Tc mirrors that on the anisotropy. Invoking the generic behavior of the anisotropy the doping dependence of the isotope effects on the critical properties, including Tc, correlation lengths and magnetic penetration depths are traced back to a change of the mobile carrier concentration.Comment: 5 pages, 3 figure

Magnetic field induced finite size effect in type-II superconductors

We explore the occurrence of a magnetic field induced finite size effect on the specific heat and correlation lengths of anisotropic type-II superconductors near the zero field transition temperature Tc. Since near the zero field transition thermal fluctuations are expected to dominate and with increasing field strength these fluctuations become one dimensional, whereupon the effect of fluctuations increases, it appears unavoidable to account for thermal fluctuations. Invoking the scaling theory of critical phenomena it is shown that the specific heat data of nearly optimally doped YBa2Cu3O7-x are inconsistent with the traditional mean-field and lowest Landau level predictions of a continuous superconductor to normal state transition along an upper critical field Hc2(T). On the contrary, we observe agreement with a magnetic field induced finite size effect, whereupon even the correlation length longitudinal to the applied field H cannot grow beyond the limiting magnetic length L(H). It arises because with increasing magnetic field the density of vortex lines becomes greater, but this cannot continue indefinitely. L(H) is then roughly set on the proximity of vortex lines by the overlapping of their cores. Thus, the shift and the rounding of the specific heat peak in an applied field is traced back to a magnetic field induced finite size effect in the correlation length longitudinal to the applied field.Comment: 8 pages, 4 figure

Magnetic field induced 3D to 1D crossover in Sr0:9La0:1CuO2

The effect of the magnetic field on the critical behavior of Sr0:9La0:1CuO2 is explored in terms of reversible magnetization data. As the correlation length transverse to the magnetic field Hi,applied along the i-axis, cannot grow beyond the limiting magnetic length LHi, related to the average distance between vortex lines, one expects a magnetic field induced finite size effect. Invoking the scaling theory of critical phenomena we provide clear evidence for this effect. It implies that in type II superconductors there is a 3D to 1D crossover line Hpi(T). Consequently, below Tc and above Hpi(T) uperconductivity is confined to cylinders with diameter LHi(1D). Accordingly, there is no continuous phase transition in the (H,T)-plane along the Hc2-lines as predicted by the mean-field treatment.Comment: 4 pages, 5 figure