Dimensional Extreme Magnetic Neutron Diffractometer
DEMAND | HB-3A | HFIR
Ultralow Sample Temperatures available at HFIR HB-3A Single-Crystal Diffractometer
Temporary removal of the chi/phi axes allows room for an orange cryostat with He-3 insert, making use of the new overhead jib crane.
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Cryostat at HB3A DEMAND Diffractometer
The cryostat has been tested at HB3A FCD and the data collected by the current 5x5cm Anger camera at 1.5 K were well fitted and consistent with the structure measured at 4 K with the regular CCR.
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Initial test of the Diamond Anvil Cell (DAC) at HFIR HB-3A
With an optimized region of interest, the background is ~ 10 cts/s. The data will be used to judge the feasibility of a future DAC experiment.
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Circular-magnetic k-vector observed on a 0.02 mm3 crystal at HFIR HB-3A
The circular distribution of k-vectors definitively confirms Fe3PO7 to have a “partially ordered” antiferromagnetic (AFM) helical state. One candidate for such a state is a short-range ordered AFM Skyrmion phase.
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Orbital selective Mott transition observed in a quasi-1D Fe-based superconductor
Neutron diffraction has revealed that two iron based ladder compounds, CsFe2Se3 and BaFe2S3, exhibit highly contrasting responses to hydraulic pressure despite their identical crystal structure and similar magnetic structures. The magnetic order in CsFe2Se3 stays unchanged up to 2 GPa, while that in BaFe2S3 undergoes a rather abrupt enhancement around 1 GPa both in transition temperature and ordered moment. Such unusual change bear the signature of an orbital-selective Mott transition.
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New magnetoelectric mechanism in a chiral-lattice antiferromagnet
Neutron scattering has shown that the spin-texture chirality in the chiral-lattice antiferromagnet MnSb2O6 is preserved when the electric polarization is reversed by the application of an external magnetic field.
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A New Direction for Iron-Based Superconductors
Single-crystal neutron diffraction is a powerful means of determining magnetic structures, and here it is used to show the parent phase of superconductors in the KxFe2-ySe2 family has a novel magnetically ordered semiconducting ground state.
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Controlling Magnetic Order by Chemical Compression
Magnetic properties of Ca1–xEuxCo2As2 vary from itinerant (3d) antiferromagnetism of Co in CaCo2As2 to the combination of itinerant (3d, Co) and localized (4f, Eu) ferromagnetism in the intermediate range to localized (4f) antiferromagnetism in Eu-rich samples.
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Localized to Strongly Correlated Electron Transition in EuCo2As2
A combination of neutron diffraction, x-ray diffraction, and heat capacity measurements in conjunction with first principles calculations were used to show that the LaCu6-xAux system hosts the first known example of an elastic quantum critical point. Neutron and x-ray diffraction measurements were performed to study the structural properties as a function of temperature and Au-composition. First principle calculations confirm that the phase transition is driven by an elastic instability and is independent of electronic properties. Heat capacity measurements indicate the presence of quantum fluctuations at the critical composition.
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Candidate Elastic Quantum Critical Point in LaCu6-xAux
A combination of neutron diffraction, x-ray diffraction, and heat capacity measurements in conjunction with first principles calculations were used to show that the LaCu6-xAux system hosts the first known example of an elastic quantum critical point. Neutron and x-ray diffraction measurements were performed to study the structural properties as a function of temperature and Au-composition. First principle calculations confirm that the phase transition is driven by an elastic instability and is independent of electronic properties. Heat capacity measurements indicate the presence of quantum fluctuations at the critical composition.
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Spin Reorientation in TlFe1.6Se2 with Complete Vacancy Ordering
A combination of neutron diffraction, x-ray diffraction, and heat capacity measurements in conjunction with first principles calculations were used to show that the LaCu6-xAux system hosts the first known example of an elastic quantum critical point. Neutron and x-ray diffraction measurements were performed to study the structural properties as a function of temperature and Au-composition. First principle calculations confirm that the phase transition is driven by an elastic instability and is independent of electronic properties. Heat capacity measurements indicate the presence of quantum fluctuations at the critical composition.
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Spin Reorientation and Magnetism in Yb14-xPrxMnSb11
An abnormal peak is observed in the dc magnetic susceptibility of Yb13.47Pr0.53MnSb11. Neutron diffraction clearly indicates that this peak is caused by a spin re-orientation of Mn moments, which is consistent with results of magnetization measurements. Refinement on the data collection also shows that moments on Mn are ordered and that moments on Pr are not.
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Polarized Neutron Diffraction at HFIR HB-3A
High neutron polarization ratio (>94%) and a good transmission (16% based on the diffraction on a 2 mm size hexaferrite crystal) enable effective polarized neutron diffraction at HB-3A. Tolerance to the horizontal focus yields double the neutron flux. 24% transmission can be achieved by moving the polarizer closer to the sample position, which requires redesigning a more compact flipper and collimator mount.
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Weak Itinerant Ferromagnetism Detected by Polarized Neutron Diffraction
High neutron polarization ratio (>95%) has been achieved at the HFIR HB-3A single crystal neutron diffractometer. This is the first use of this capability on an experiment approved through the General User program. We succeeded in detecting a weak itinerant ferromagnetic moment of 0.11(1)μB/atom on a NiCoCr0.6 crystal with an effective mass of 20 mg.
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The ordered low-dimensional frustrated magnets challenge the nonlinear spin-wave theories
Results on an ordered low dimensional frustrated magnet suggest a new theoretical framework is needed for adequate description.
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SPICE upgrade for HB-3A 2D detector
Added cursors to identify each pixel ID, corresponding hkl, and received neutron counts. New function to let users define Region of Interests. Instrument configuration is written in each measured data. Improved capability for optimizing the data collections. Monitor was better synchronized through HFIRLITE
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Itinerant Antiferromagnetism in RuO2
Rutile-type RuO2 had been considered a Pauli paramagnet, until this report demonstrated a previously undetected lattice distortion below approximately 900 K accompanied by antiferromagnetic order. The room temperature magnetic moment of approximately 0.05 μB is small, but clearly confirmed by polarized neutron diffraction. This experiment and corresponding theory suggest that the combination of high Néel temperature and small itinerant moments in RuO2 are unique among metallic oxides.
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