Neutron Scattering Experiment on Magnetic Field Effect in Under-doped Superconducting BaFe$_{1.915}$Ni$_{0.085}$As$_{2}$

In under-doped BaFe$_{2-X}$(Ni,Co)$_{X}$As$_{2}$, superconductivity coexist with the anti-ferromagnetic (AFM) order. By applying a $\sim $10 Tesla magnetic field parallel to a-b plan, we performed a series of elastic and inelastic neutron scattering measurement on BT-7 instrument in NCNR, NIST. We measured how magnetic bragg-peaks and spin excitation in BaFe$_{1.915}$Ni$_{0.085}$As$_{2}$ will change upon the change of the field.