X-ray Diffraction In Magnetic Fields Research Articles

High magnetic field x-ray diffraction study of the α phase of solid oxygen: Absence of giant magnetostriction

High magnetic field x-ray diffraction experiments of solid oxygen have been performed at 10 K using DC magnetic fields of up to 5 T as well as pulsed magnetic fields of up to 25 T. The $\ensuremath{\alpha}$ phase of oxygen exhibits no magnetostriction greater than $\mathrm{\ensuremath{\Delta}}d/d={10}^{\ensuremath{-}4}$ at 5 T, where $d$ and $\mathrm{\ensuremath{\Delta}}d$ denote a lattice plane spacing and its magnetic field variation, respectively. The $\mathrm{\ensuremath{\Delta}}d/d$ at higher fields of up to 25 T is found to be smaller than $2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$. These results contradict the previously reported giant magnetostriction in the $\ensuremath{\alpha}$ phase where the volume magnetostriction $\mathrm{\ensuremath{\Delta}}V/V$ reaches ${10}^{\ensuremath{-}2}$ at 7.5 T [K. Katsumata et al., J. Phys.: Condens. Matter 17, L235 (2005)].

A facility for X-ray diffraction in magnetic fields up to 25 T and temperatures between 15 and 295 K.

A facility for X-ray diffraction has been developed at the National High Magnetic Field Laboratory. It brings diffraction capability to the 25 T Florida split coil magnet and implements temperature control in a range of 15-295 K using a cold finger helium cryostat. This instrument represents an alternative to pulsed magnetic field systems, and it exceeds the static magnetic fields currently available at synchrotron facilities. Magnetic field compatibility of an X-ray source and detectors with the sizable magnetic fringe fields emanating from the magnet constrained the design of the diffractometer.

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.

Evidence for hidden quadrupolar fluctuations behind the octupole order inCe0.7La0.3B6from resonant x-ray diffraction in magnetic fields

The multipole ordered phase in Ce${}_{0.7}$La${}_{0.3}$B${}_{6}$, emerging below 1.5 K and named phase IV, has been studied by resonant x-ray diffraction in magnetic fields. By utilizing diamond x-ray phase plates to rotate the incident linear polarization and a conventional crystal analyzer system, full linear polarization analysis has been performed to identify the order parameters. The analysis shows that the ${\ensuremath{\Gamma}}_{5g}$ (${O}_{yz}$, ${O}_{zx}$, ${O}_{xy}$) quadrupoles are more induced by the field than the ${\ensuremath{\Gamma}}_{3g}$ (${O}_{20}$ and ${O}_{22}$) quadrupoles on the ${\ensuremath{\Gamma}}_{5u}$ (${T}_{x+y+z}^{\ensuremath{\beta}}$) antiferro-octupole order in phase IV. The problem is that this result is contradictory to a mean-field calculation, which inevitably gives the ${\ensuremath{\Gamma}}_{3g}$ quadrupole as the main induced moment. This result indicates that the ${\ensuremath{\Gamma}}_{5g}$ quadrupole order is close in energy. We consider that a large fluctuation of the ${\ensuremath{\Gamma}}_{5g}$ quadrupole is hidden behind the primary ordering of the ${\ensuremath{\Gamma}}_{5u}$ octupole and that the multipolar fluctuation significantly affects the ordering phenomenon.

Behavior of the Antiferroquadrupolar Moments in the Antiferromagnetic Ordered Phase of CeB6

We have studied the variation of the antiferroquadrupolar order parameters in the antiferromagnetic ordered phase of CeB 6 by means of resonant and non-resonant x-ray diffraction in magnetic fields. From the magnetic field dependences of the intensities, we argue that the quadrupolar order parameter is gradually reoriented to the linear combination state depending on the field direction.

Direct observation of field-induced variant transformation in Fe3Pt using pulsed magnetic field x-ray diffraction

X-ray diffraction experiments in pulsed magnetic fields were performed to study the giant magnetic-field-induced strain in the martensitic phase of ordered Fe3Pt alloy. The field dependence of the arrangement of the variants (crystallographic domains) was observed directly in pulsed magnetic fields for the first time. The variants with the c axis perpendicular to the magnetic field are transformed into variants with the c axis nearly parallel to the magnetic field. Moreover, we found that the reorientation behaviors are different for different variants with the same crystallographic direction. The results demonstrate the crucial importance of microscopic investigation, such as x-ray diffraction analysis, of the martensitic transition. We also found that the magnetic-field-induced strain associated with the rearrangement of the variants occurs even in a very fast sweeping pulsed field of up to 1.9×103 T/s at 1 T.

Low temperature and magnetic field X-ray diffraction study for Nd 0.5Sr 0.5MnO 3

First-order structural phase transition based on charge order for Nd 0.5Sr 0.5MnO 3 was studied by a newly developed low temperature and magnetic field X-ray diffraction apparatus. The structural phase transition that corresponds to a jump of lattice constants was confirmed even in magnetic fields up to 5 T. We observed the coexistence region consisting of high and low-temperature phases in magnetic fields. This region increased with increasing field. The domain of the high-temperature ferromagnetic phase remains in the charge order phase at low temperature and low magnetic field. The magnetic behavior is explained by the volume fraction of high-temperature domain.

X-ray-scattering study of the charge-density-wave structure inNbSe3in high magnetic fields

An upper bound of $\ensuremath{\Delta}q/ql~2.5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$ on the magnetic-field-induced shift of the wave vector of the low-temperature charge-density wave in ${\mathrm{NbSe}}_{3}$ is established by high-resolution x-ray diffraction in magnetic fields up to 10 T. The charge-density-wave order parameter is also magnetic-field independent, to within 10%. These limits are discussed in the context of magnetotransport experiments on ${\mathrm{NbSe}}_{3}$ as well as theoretical models that had predicted a magnetic-field dependence of the charge-density-wave structure.

X-ray diffraction in magnetic fields

A method to determine the direction of magnetization in polycrystalline materials was developed using X-ray powder diffraction under an external magnetic field. The application of the magnetic field to the powdered sample induces a preferred orientation. By observing the changes in the line intensities as a consequence, the direction of spontaneous magnetization within the lattice can be determined in the case of a ferro- or ferrimagnetic arrangement. Since the sample holder with the permanent magnet is mounted on the cold tinger of a flow cryostal, it is also possible to observe a change in direction of spontaneous magnetization as a function of the temperature.

Direct observation of a magnetic field induced commensurate-incommensurate transition in a spin-Peierls system.

Using high resolution x-ray diffraction in magnetic fields up to 12.5 T, we have directly observed a magnetic field driven commensurate-incommensurate transition in a spin-Peierls compound, the organic charge transfer salt tetrathiafulvalene-Cu-bis-dithiolene (TTF-CuBDT). The field induced transition is weakly first order. The period of the incommensurate lattice modulation in the high field phase is consistent with theoretical predictions.