[en] The current status of the pulsed-magnet program of the Dresden High Magnetic Field Laboratory (HLD) is reported. The non-destructive pulsed magnets for the HLD include a wide spectrum of coils designed for energies between 1 and 46MJ, magnetic fields of 60 - 100T, and pulse durations of 10 - 1000 ms. Various experimental techniques at pulsed magnetic fields will be available for external users soon. Some user magnets for first scientific experiments have been installed and tested. A 8.5MJ/70 T mono-coil magnet has been built and first test results for this magnet are presented. The design of a two-coil 46 MJ magnet for magnetic fields above 85T has been completed. This magnet is under construction now. Important issues of the coil design are numerical simulations of the pulsed-magnet performance. Both analytical approaches and finite-element analysis are used for these simulations at the HLD

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[en] Magnetization measurements of the superconducting (T_c approx47 K) and magnetically ordered (T_M^Ru∼130 K) RuSr₂GdCu₂O₈ (Ru1212) have been performed in pulsed magnetic fields up to 47 T. The average Ru-moment, determined by using NbSr₂GdCu₂O₈ as reference, is 1.8 μ_B suggesting that the investigated sample is in a mixed valence state containing 87% Ru⁵⁺ (2 μ_B) and 13% Ru⁴⁺ (0.9 μ_B). This ratio is consistent with an underdoped nature of the superconducting state with a hole concentration in the CuO₂ plane of p∼0.065. It is suggested that the magnetic structure of Ru1212 consists of a main antiferromagnetic phase formed by Ru⁵⁺ ions interrupted by ferromagnetic stripes, where double exchange between Ru⁵⁺ and Ru⁴⁺ ions takes place. Different Ru⁵⁺/Ru⁴⁺ ratios, due to different preparation conditions, could explain some of the diverse superconducting and magnetic properties reported in the literature for Ru1212. (orig.)

[en] We report on studies on the magnetic and magnetoacoustic properties of uranium intermetallic antiferromagnets UCo₂Si₂, UCu_0.95Ge, UIrGe and U₂Ni₂Sn in pulsed magnetic fields up to 60 T, where they undergo metamagnetic transitions. The measurements were performed in the temperature range from 1.4 to 100 K. The magnetic ordering and the metamagnetic transitions are accompanied by pronounced anomalies in the ultrasound velocity and the ultrasound attenuation. All studies were performed on single crystals grown by the Czochralski method in a tri-arc furnace.

[en] Tetragonal UPt₂Si₂ has been characterized as a moderately mass enhanced antiferromagnetic compound (T_N=32 K), which in low magnetic fields resembles other materials such as URu₂Si₂. Here,we present an extensive study of resistivity and magnetization of single crystalline UPt₂Si₂ in high magnetic fields up to 50 T. Initially we find the phase transition at T_N=32 K in zero field to shift down to lower temperatures with increasing field for both crystallographic axes. Below ∝ 15 K and for B//a we see this transition to split up and become hysteretic, forming a new and distinct high field phase between ∝38T and ∝45 T. Similarly, with B//c we also find a splitting resulting in a new high field phase between ∝24 T and ∝31 T. Moreover, below 5 K our measurements along the c axis show even more structure, indicating at least one more high field phase between ∝29 T and ∝33 T. Altogether, our data reveal a rich magnetic high field phase diagram, which resembles some observations made for URu₂Si₂.

[en] We report on high-field magnetization, specific heat, and electron-spin-resonance (ESR) studies of the quasi-two-dimensional spin-1/2 Heisenberg antiferromagnet (Cu(pyz)₂(HF₂))PF₆. The frequency-field diagram of ESR modes below T_N = 4.38 K is described in the frame of the mean-field theory, confirming a collinear magnetic structure with an easy-plane anisotropy. The obtained results allowed us to determine the anisotropy/exchange interaction ratio, A/J = 0.003, and the upper limit for the interplane/intraplane exchange interaction ratio, J'/J = 1/16. It is argued that despite the onset of three-dimensional long-range magnetic ordering the magnetic properties of this material (including high-magnetic-field magnetization and nonmonotonic field dependence of the Neel temperature) are strongly affected by two-dimensional spin correlations.

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[en] Comparative experiments between the two semimetals CeBiPt and LaBiPt reveal changes of the Fermi surface in CeBiPt with respect to temperature, applied magnetic, field and chemical composition. It must be concluded that the strong temperature dependence of the Shubnikov-de Haas (SdH) frequency as well as the change of carrier concentration above a sample dependent critical field are associated with the 4f electrons introduced by the Ce atoms. We present Hall and magnetoresistance measurements up to 70 T obtained at our new pulsed high magnetic field laboratory in Dresden. We observe the disappearance of the SdH signal and a change of the Hall coefficient above a sample-dependent threshold field. Rather than at 25 T, as reported previously, we measured a threshold field of ∼40 T demonstrating the strong dependence of the Fermi surface on stoichiometry. (orig.)

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No abstract available