Mössbauer measurement of the hyperfine magnetic field AT sp site in Heusler alloys Rh2 Mn Z (Z=In and Sb)

We have investigated the systematics of hyperfine magnetic field on a fixed probe at the Z-site in Heusler alloys Rh₂MnZ as the valence of Z (sp element) is varied. The hmf on¹¹⁹Sn in Rh₂MnIn_.98 ¹¹⁹Sn₀₂ has been measured at 293K and 77K. In Rh₂Mn_1.12Sb_.86 ¹¹⁹Sn_.02 the hmf on¹²¹Sb has been measured at 77 K, and on¹¹⁹Sn at 293 K and 77 K. The results are compared with the hmf on¹¹⁹Sn in Rh₂Mn Ge_.98 ¹¹⁹Sn_.02 Rh₂Mn Sn, and Rh₂Mn Pb_.98 ¹¹⁹Sn_.02.Supported by the University Research Council, University of CincinnatiSupported by the Natural Sciences and Engineering Research Council of Canada     

Wave scattering effects in elastic percolation models

The study of the propagation of waves in randomly diluted models is presented. Porosity (crack-like) models are simulated by constructing typical elastic percolation networks with random microscopic heterogeneities in order to resemble rock media. Central and bond-bending forces (Born Hamiltonian) models are considered. For each experimental case, the elastic energy of the system is relaxed in equilibrium and then the model is excited by a pulse source in order to produce wave propagation. First, a review is presented of the well established velocity-porosity relationship from rock physics, which shows a linear trend from small porosities up to the critical porosity (percolation threshold) where the rocks fall apart. From the wave propagation analysis a general trend is observed for the attenuation of waves, from the small to the large porosity models, suggesting multiple scattering effects similar to those reported from effective-medium approximations of wave scattering due to random heterogeneities. Finally, the results are compared with those obtained from laboratory experiments on dry rocks with different porosities and different applied stress regimes.     

Sn hyperfine field trends in the Heusler alloys Co2Mn(Al,Si)

Hyperfine Interactions - The Sn hyperfine field in the series of Heusler alloys Co2MnAl0.98−xSixSn0.02 (x=0.00, 0.20, 0.40, 0.58, 0.78, 0.98) has been measured at 77 K using119Sn...     

Effects of rapid quenching on the structural and magnetic properties of the Heusler alloy Cu2MnSn

The Heusler alloy Cu₂MnSn has been prepared by two methods; (1) the conventional method of annealing for an extended period of time just below the melting temperature, followed by quenching into ice water, and (2) rapid quenching from the melt onto the surface of a rotating Cu disc. X-ray diffraction and ¹¹⁹Sn Mössbauer effect measurements show that the annealed sample contains a significant quantity of a non-magnetic impurity phase while the rapidly quenched sample is essentially free from non-Heusler phases.     

Three-dimensional magneto-optic trap for micro-object manipulation

A magneto-optic trap for micro-objects is described. Magnetic beads were trapped by optical tweezers while being rotated by a new integrated magnetic manipulator. Rotation was achieved with eight electromagnets with tip-pole geometry. The time orbital potential technique was used to achieve rotation of magnetic beads. Trapping in three dimensions and rotation of magnetic beads on three axes are demonstrated with forces up to 230 pN and force momenta of up to 10(-16)N m . A position-detection apparatus based on an interferometric scheme provides nanometer sensitivities in a few milliseconds.     

Mössbauer study of Er3+ in ErH3 and YH3

The Mössbauer spectra of ¹⁶⁶Er in ErH₃ and YH₃ have been measured. Using and axial Hamiltonian, the electronic gyromagnetic rations for the ground state of Er³⁺ in YH₃ have been deduced: g| = 11.6 ± 0.1 and g⊥ = 4.4 ± 0.1. The analysis yields crystal field parameters which provide the correct λ₇ ground state with these g-values.     

On the bond breaking model of polyatomic ion emission in secondary ion mass spectrometry

The cluster size distribution (number of clusters versus number of atoms in the cluster) resulting from a simple nearest neighbor Bond Breaking Model (BBM) of Secondary Ion Mass Spectroscopy (SIMS) is studied for one- and two-dimensional and Bethe lattices. In one dimension, the distribution is monotonic. In two dimensions, however, irregularities can occur as a function of the probability β of breaking any given bond. These irregularities differentiate between square, honeycomb, and triangular lattices and are most pronounced if the overall probability of breaking any bond in the lattice is small.