Lukas Keller

Neutron diffraction at SINQ

Abstract The high resolution powder diffractometer for thermal neutrons, HRPT, with 1600 detectors (PSD) started operation in 1999 at the SINQ target station [1]. For 20, = 120° and a sample diameter of 10 mm already, resolutions down to δ/d < 0.001 (d = lattice spacing) were reached. As an example, Figure 1 shows a precise determination of deuterium positions for the metal deuteride Cs,MgD, [2]. Figure 2 illustrates the detection of rather small structural distortions in the case of HOB, at low temperatures [3].

Dipolar Antiferromagnetism and Quantum Criticality in LiErF4

Dropping a Dimension? In most magnetic materials, the exchange interaction causes the spins on the neighboring sites of a crystal lattice to align. In the absence of exchange interactions, dipolar interactions, which are highly orientation dependent, are also expected to be able to cause magnetism. Kraemer et al. (p. 1416) present evidence for antiferromagnetism in a dipolar-coupled material, LiErF4. Although a three-dimensional system, its critical behavior was more reminiscent of a two-dimensional material. Scattering experiments reveal that magnetic ordering can arise from dipolar interactions, not only from exchange. Magnetism has been predicted to occur in systems in which dipolar interactions dominate exchange. We present neutron scattering, specific heat, and magnetic susceptibility data for LiErF4, establishing it as a model dipolar-coupled antiferromagnet with planar spin-anisotropy and a quantum phase transition in applied field Hc|| = 4.0 ± 0.1 kilo-oersteds. We discovered non–mean-field critical scaling for the classical phase transition at the antiferromagnetic transition temperature that is consistent with the two-dimensional XY/h4 universality class; in accord with this, the quantum phase transition at Hc exhibits three-dimensional classical behavior. The effective dimensional reduction may be a consequence of the intrinsic frustrated nature of the dipolar interaction, which strengthens the role of fluctuations.

Pressure effects on the magnetic structure in La 0.5 Ca 0.5 − x Sr x MnO 3 ( 0.1 ≤ x ≤ 0.4 ) manganites

The effect of high pressure (0char21{}8 GPa) on the magnetic structure of polycrystalline samples of

Interparticle interactions in composites of nanoparticles of ferrimagnetic (γ-Fe2O3) and antiferromagnetic (CoO,NiO) materials

{text{La}}_{0.5}{text{Ca}}_{0.5ensuremath{-}x}{text{Sr}}_{x}{text{MnO}}_{3}

Magnetic ordering and spin-reorientation transitions in TbCo{sub 3}B{sub 2}

(0.1ensuremath{le}xensuremath{le}0.4)

Magnetic order in CeI 2

manganites at 5 K is investigated using neutron-diffraction technique. Application of pressure is found to modify the previously reported magnetic structure, observed under ambient conditions, in these compounds [I. Dhiman et al., Phys. Rev. B 77, 094440 (2008)]. In

In-situ neutron diffraction study of thermal phase stability in a γ-TiAl based alloy doped with Mo and/or C

x=0.1

Relative orientation of the magnetic moments in modulated multiferroic CaMn7O12

composition, at 4.6(2) GPa and beyond,

Spin reorientation in α-Fe2O3 nanoparticles induced by interparticle exchange interactions in alpha-Fe2O3/NiO nanocomposites

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