Ni-base superalloy single crystal (SX) mosaicity characterized by the Rotation Vector Base Line Electron Back Scatter Diffraction (RVB-EBSD) method.

In the present work we present the Rotation Vector Base Line Electron Back Scatter Diffraction (RVB-EBSD) method, a new correlative orientation imaging method for scanning electron microscopy (OIM/SEM). The RVB-EBSD method was developed to study crystal mosaicity in as-cast Ni-base superalloy single crystals (SX). The technique allows to quantify small crystallographic deviation angles between individual dendrites and to interpret associated accommodation processes in terms of geometrically necessary dislocations (GNDs). The RVB-EBSD method was inspired by previous seminal approaches which use cross correlation EBSD procedures. It applies Gaussian band pass filtering to improve the quality of more than 500 000 experimental patterns. A rotation vector approximation and a correction procedure, which relies on a base line function, are used. The method moreover features a novel way of intuitive color coding which allows to easily appreciate essential features of crystal mosaicity. The present work describes the key elements of the method and shows examples which demonstrate its potential.

Nature of the spin dynamics and 1/3 magnetization plateau in azurite.

We present a specific heat and inelastic neutron scattering study in magnetic fields up into the 1/3 magnetization plateau phase of the diamond chain compound azurite Cu3(CO3)2(OH)2. We establish that the magnetization plateau is a dimer-monomer state, i.e., consisting of a chain of S=1/2 monomers, which are separated by S=0 dimers on the diamond chain backbone. The effective spin couplings Jmono/kB=10.1(2) K and Jdimer/kB=1.8(1) K are derived from the monomer and dimer dispersions. They are associated to microscopic couplings J1/kB=1(2) K, J2/kB=55(5) K and a ferromagnetic J3/kB=-20(5) K, possibly as result of dz2} orbitals in the Cu-O bonds providing superexchange (SE) pathways with JSE=6.5 K.