A 31 T split-pair pulsed magnet for single crystal x-ray diffraction at low temperature.

We have developed a pulsed magnet system with panoramic access for synchrotron x-ray diffraction in magnetic fields up to 31 T and at low temperature down to 1.5 K. The apparatus consists of a split-pair magnet, a liquid nitrogen bath to cool the pulsed coil, and a helium cryostat allowing sample temperatures from 1.5 up to 250 K. Using a 1.15 MJ mobile generator, magnetic field pulses of 60 ms length were generated in the magnet, with a rise time of 16.5 ms and a repetition rate of 2 pulses/h at 31 T. The setup was validated for single crystal diffraction on the ESRF beamline ID06.

Tunnel diode oscillator measurements of the upper critical magnetic field of FeTe(0.5)Se(0.5).

Temperature dependence of the upper critical magnetic field (Hc2) of single crystalline FeTe0.5Se0.5(Tc = 14.5 K) have been determined by tunnel diode oscillator-based measurements in magnetic fields of up to 55 T and temperatures down to 1.6 K. The Werthamer-Helfand-Hohenberg model accounts for the data for magnetic field applied both parallel (H ‖ ab) and perpendicular (H ‖ c) to the iron conducting plane, in line with a single band superconductivity. Whereas Pauli pair breaking is negligible for H ‖ c, Pauli contribution is evidenced for H ‖ ab with Maki parameter α = 1.4, corresponding to Pauli field HP = 79 T. As a result, the Hc2 anisotropy [Formula: see text] which is already rather small at Tc (γ = 1.6) further decreases as the temperature decreases and becomes smaller than 1 at liquid helium temperatures.

Magnetic structure of phase II in U(Ru(0.96)Rh(0.04))2Si2 determined by neutron diffraction under pulsed high magnetic fields.

We report neutron diffraction measurements on U(Ru(0.96)Rh(0.04))(2)Si(2) single crystal under pulsed high magnetic fields up to 30 T applied along the tetragonal c axis. The high-field experiments revealed that the field-induced phase II above 26 T corresponds to a commensurate up-up-down ferrimagnetic structure characterized by the wave vector q=(2/3,0,0) with the magnetic moments parallel to the c axis, which naturally explains the one-third magnetization plateau and the substantially changed Fermi surface in phase II. This a-axis modulated magnetic structure indicates that the phase II near the hidden order phase is closely related to the characteristic incommensurate magnetic fluctuations at Q(1)=(0.6,0,0) in the pure system URu(2)Si(2), in contrast to the pressure-induced antiferromagnetic order at Q(0)=(1,0,0).

Spin-lattice coupling, frustration, and magnetic order in multiferroic RMnO3.

We have performed high-resolution neutron diffraction and inelastic neutron scattering experiments in the frustrated multiferroic hexagonal compounds RMnO_{3} (R = Ho,Yb,Sc,Y), which provide evidence of a strong magnetoelastic coupling in the whole family. We can correlate the atomic positions, the type of magnetic structure, and the nature of the spin waves whatever the R ion and temperature. The key parameter is the position of the Mn ions in the unit cell with respect to a critical threshold of 1/3, which determines the sign of the coupling between Mn triangular planes.