Electric field and photo-excited control of the carrier concentration in GdN

We present both electric-field and photo-excited control of the carrier concentration in GdN. There is no evidence in the results of a carrier-mediated contribution to the Gd-Gd exchange interaction that has been suggested to explain a measured Curie temperature that is much higher than obtained within theoretical treatments. Persistent carrier concentrations seen in both the field-effect and photo-induced conductivities point to a distribution of long-lived trap states below the conduction band, very likely centred at nitrogen vacancie

Problemática asociada a los cambios de uso del suelo : zona irrigada del Departamento de San Rafael, Mendoza

El Departamento de San Rafael, se encuentra en un territorio de alta fragilidad por las características que posee. Los cambios en el uso del suelo en este tipo de zonas causan diversos problemas y conflictos con los componentes del territorio. Los objetivos del trabajo son analizar los cambios de uso del suelo y la relación con la legislación vigente y describir la problemática asociada. A través del análisis espacial con Google Earth se ha realizado relevamientos de zonas con cambio de uso del suelo. En el Departamento, el abandono de fincas debido a la situación crítica que sufre el sector agrícola ha traído aparejada consecuencias negativas en la red de riego y un cambio de uso del suelo creciente hacia usos residenciales y turísticos. El recurso hídrico es uno de los factores más afectados tanto en su uso como distribución.The Department of San Rafael, is a territory of high fragility by the characteristics that it possesses. Changes in land use in areas of high environmental fragility cause various problems and conflicts with the components of the territory. The objectives of this work are to analyze changes in land use and the relationship with current legislation and describe the associated problems. Through the spatial analysis with Google Earth has been made surveys of areas with land use change. In the Department, the abandonment of the farms by a critical situation that suffers the agricultural sector. This has brought about the appearance of negative consequences on red irrigation, a change of land use for residential and tourist uses. The water resource is one of the factors most affected both in its use and distribution.Fil: Guajardo, Adriana B.. Universidad Nacional de Cuyo. Facultad de Ciencias Aplicadas a la IndustriaFil: Alcantú, Stella M.. Universidad Nacional de Cuyo. Facultad de Ciencias Aplicadas a la IndustriaFil: Giaroli, Gisela Natali. Universidad Nacional de Cuyo. Facultad de Ciencias Aplicadas a la IndustriaFil: Rodríguez, María B.. Universidad Nacional de Cuyo. Facultad de Ciencias Aplicadas a la IndustriaFil: Vega, Gustavo. Universidad Nacional de Cuyo. Facultad de Ciencias Aplicadas a la Industri

Highly resistive epitaxial Mg-doped GdN thin films

We report the growth by molecular beam epitaxy of highly resistive GdN, using intentional doping with magnesium. Mg-doped GdN layers with resistivities of 1000 {\Omega}.cm and carrier concentrations of 10E16 cm-3 are obtained for films with Mg concentrations up to 5 x 10E19 atoms/cm3. X-ray diffraction rocking curves indicate that Mg-doped GdN films have crystalline quality very similar to undoped GdN films, showing that the Mg doping did not affect the structural properties of the films. A decrease of the Curie temperature with decreasing the electron density is observed, supporting a recently suggested magnetic polaron scenario [F. Natali et al., Phys. Rev. B 87, 035202 (2013)]

Spin/orbit moment imbalance in the near-zero moment ferromagnetic semiconductor SmN

SmN is ferromagnetic below 27 K, and its net magnetic moment of 0.03 Bohr magnetons per formula unit is one of the smallest magnetisations found in any ferromagnetic material. The near-zero moment is a result of the nearly equal and opposing spin and orbital moments in the 6H5/2 ground state of the Sm3+ ion, which leads finally to a nearly complete cancellation for an ion in the SmN ferromagnetic state. Here we explore the spin alignment in this compound with X-ray magnetic circular dichroism at the Sm L2,3 edges. The spectral shapes are in qualitative agreement with computed spectra based on an LSDA+U (local spin density approximation with Hubbard-U corrections) band structure, though there remain differences in detail which we associate with the anomalous branching ratio in rare-earth L edges. The sign of the spectra determine that in a magnetic field the Sm 4f spin moment aligns antiparallel to the field; the very small residual moment in ferromagnetic SmN aligns with the 4f orbital moment and antiparallel to the spin moment. Further measurements on very thin (1.5 nm) SmN layers embedded in GdN show the opposite alignment due to a strong Gd-Sm exchange, suggesting that the SmN moment might be further reduced by about 0.5 % Gd substitution

Optomechanical sideband cooling of a thin membrane within a cavity

We present an experimental study of dynamical back-action cooling of the fundamental vibrational mode of a thin semitransparent membrane placed within a high-finesse optical cavity. We study how the radiation pressure interaction modifies the mechanical response of the vibrational mode, and the experimental results are in agreement with a Langevin equation description of the coupled dynamics. The experiments are carried out in the resolved sideband regime, and we have observed cooling by a factor 350 We have also observed the mechanical frequency shift associated with the quadratic term in the expansion of the cavity mode frequency versus the effective membrane position, which is typically negligible in other cavity optomechanical devices.Comment: 15 pages, 7 figure

Europium nitride: A novel diluted magnetic semiconductor

Europium nitride is semiconducting and contains non-magnetic \3+, but sub-stoichiometric EuN has Eu in a mix of 2+ and 3+ charge states. We show that at \2+ ~concentrations near 15-20% EuN is ferromagnetic with a Curie temperature as high as 120 K. The \3+ ~polarization follows that of the \2+, confirming that the ferromagnetism is intrinsic to the EuN which is thus a novel diluted magnetic semiconductor. Transport measurements shed light on the likely exchange mechanisms.Comment: 5 page

Superconductivity in the ferromagnetic semiconductor SmN

The discovery of materials that simultaneously host different phases of matter has often initially confounded, but ultimately enhanced, our basic understanding of the coexisting types of order. The associated intellectual challenges, together with the promise of greater versatility for potential applications, have made such systems a focus of modern materials science. In particular, great efforts have recently been devoted to making semiconductors ferromagnetic and metallic ferromagnets superconducting. Here we report the unprecedented observation of a heavily donor-doped ferromagnetic semiconductor, SmN, becoming superconducting with ferromagnetism remaining intact. The extremely large exchange splitting of the conduction and valence bands in this material necessitates that the superconducting order hosted by SmN is of an unconventional triplet type, most likely exhibiting p-wave symmetry. Short range spin fluctuations, which are thought to be the cause of pairing interactions in currently known triplet superconductors, are quenched in SmN, suggesting its superconductivity to be the result of phonon- or Coulomb-mediated pairing mechanisms. This scenario is further supported by the inferred heavy mass of superconducting charge carriers. The unique near-zero magnetisation associated with the ferromagnetic state in SmN further aids its coexistence with superconductivity. Presenting this novel material system where semiconducting, ferromagnetic and superconducting properties are combined provides a versatile new laboratory for studying quantum phases of matter. Moreover it is a major step towards identifying materials that merge superconductivity and spintronics, urgently needed to enable the design of electronic devices with superior functionality.Comment: 8 pages, 5 figures, main text plus supplemental materia