Transport properties of microstructured ultrathin films of La0.67Ca0.33MnO3 on SrTiO3

We have investigated the electrical transport properties of 8 nm thick La0.67Ca0.33MnO3 films, sputter-deposited on SrTiO3 (STO), and etched into 5 micrometer-wide bridges by Ar-ion etching. We find that even slight overetching of the film leads to conductance of the STO substrate, and asymmetric and non-linear current-voltage (I-V) characteristics. However, a brief oxygen plasma etch allows full recovery of the insulating character of the substrate. The I-V characteristics of the bridges are then fully linear over a large range of current densities. We find colossal magnetoresistance properties typical for strained LCMO on STO but no signature of non-linear effects (so-called electroresistance) connected to electronic inhomogeneites. In the metallic state below 150 K, the highest current densities lead to heating effects and non-linear I-V characteristics.Comment: 3 pages, 5 figure

In Search of Parity: Child Custody/Visitation and Child Support for Lesbian Couples Under “Companion” Cases Debra H. and In Re H.M.

The United States is engaged in a national debate over whether to grant same-sex couples the rights and privileges of marriage. Supporters of marriage equality flood the media with images of jubilant same-sex couples simply wanting the chance to say their “I dos” and have the state formally recognize their shared love and commitment. The unfortunate reality is, however, that many homosexual relationships, like heterosexual relationships, dissolve. Marriage rights play as important a role at a relationship’s dissolution as they do at a relationship’s inception. This paper focuses on one such issue often left out of the public discourse over marriage equality: determining parentage for the purposes of child custody/visitation as well as child support in the context of a lesbian relationship that has broken down.Looking at two recent cases from the New York Court of Appeals, Debra H. and H.M. together, one can clearly see an alarming development: eliminating the applicability of equitable principles to provide legal parental status for a non-biological, non-adoptive parent to contest custody/visitation, while at the same time relying on such principles to force child support payments on the same individuals. Child visitation jurisprudence and child support jurisprudence should stand in parity, making it so an individual would simply be adjudicated a parent, not a parent solely for contesting child custody/visitation or a parent solely for child support. Otherwise, not only is the best interest of the child lost, but so too is the principle of fundamental fairness on the part of the defendant partner. In addition to drawing attention to this alarming jurisprudential development, I also set for alternate, substantive solutions

Strain, size and field effects in (La, Ca)MnO3 thin films

Doped manganese oxides such as La0.67Ca0.33MnO3 (LCMO) are strongly correlated electron systems which display an insulator to metal transition upon cooling at a temperature T_MI. At low temperature the material is ferromagnetic. Above the transition the material is a paramagnetic insulator in which conduction is governed by activated polaron hopping. As yet, the fundamental question of conductance on micrometer length scales (the scale on which electronic phase separation can occur) has been little studied. We investigate this question of electrical transport in LCMO, which requires the fabrication of micron sized structures in LCMO thin films. We measure current-voltage (I-V) characteristics as function of temperature, in high magnetic fields, in electric fields and with varying film thickness. In warming from the metallic to the insulating state we find strong non-linear effects in the steep part of the transition. The differential resistance is largest at zero bias, then drops with increasing current, and saturates at a current density which is the same for different samples. Resistance drops of up to 80 % are observed upon increasing the applied current. We propose that the nonlinear behavior is a direct signature of an intervening phase involving the formation of short range polaron correlations (electron-glass). The nonlinear behavior occurs when the homogeneous glass phase which now encompasses the entire microstructure is melted by the applied electrical current. We also associate the formation of inhomogeneities in the microstructure with the appearance of a strong electric field effect.LEI Universiteit LeidenCondensed Matter Condensed Physic