Interdependence of magnetism and superconductivity in the borocarbide TmNi2B2C

We have discovered a new antiferromagnetic phase in TmNi2B2C by neutron diffraction. The ordering vector is Q_A = (0.48,0,0) and the phase appears above a critical in-plane magnetic field of 0.9 T. The field was applied in order to test the assumption that the zero-field magnetic structure at Q_F = (0.094,0.094,0) would change into a c-axis ferromagnet if superconductivity were destroyed. We present theoretical calculations which show that two effects are important: A suppression of the ferromagnetic component of the RKKY exchange interaction in the superconducting phase, and a reduction of the superconducting condensation energy due to the periodic modulation of the moments at the wave vector Q_A

Deep far infrared ISOPHOT survey in "Selected Area 57", I. Observations and source counts

We present here the results of a deep survey in a 0.4 sq.deg. blank field in Selected Area 57 conducted with the ISOPHOT instrument aboard ESAs Infrared Space Observatory (ISO) at both 60 um and 90 um. The resulting sky maps have a spatial resolution of 15 x 23 sq.arcsec. per pixel which is much higher than the 90 x 90 sq.arcsec. pixels of the IRAS All Sky Survey. We describe the main instrumental effects encountered in our data, outline our data reduction and analysis scheme and present astrometry and photometry of the detected point sources. With a formal signal to noise ratio of 6.75 we have source detection limits of 90 mJy at 60 um and 50 mJy at 90 um. To these limits we find cumulated number densities of 5+-3.5 per sq.deg. at 60 um and 14.8+-5.0 per sq.deg.at 90 um. These number densities of sources are found to be lower than previously reported results from ISO but the data do not allow us to discriminate between no-evolution scenarios and various evolutionary models.Comment: 15 pages, 11 figures, accepted by Astronomy & Astrophysic

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Magnetic and quadrupolar ordering in TmNi2B2C

We present neutron and high energy synchrotron X ray diffraction studies to show that the anomalous antiferromagnet AF phase diagram of TmNi2B2C in an applied field along [100] is governed by a quadrupolar ordering of the Tm ion