Magnetization and Specific Heat Investigations of the Bose Glass: Br-doped NiCl$_{2}$-4SC(NH$_{2}$)$_{2}$

NiCl$_{2}$-4SC(NH$_{2})_{2}$ (DTN) is an insulating material, which shows field induced XY-AFM order between $H_{c1}$ = 2.1 T and $H_{c2}$ = 12.6 T. In boson language, the ground state of DTN can be described as a Mott insulator, and the ordered state as a Bose-Einstein condensation of magnons. Bond disorder is introduced by substituting Br atoms on Cl positions, which simultaneously changes the super exchange interaction along the $c$-direction on a local scale and leads to a Mott-glass ground state in zero field. Furthermore, the system develops a gapless Bose glass for magnetic fields 0 $< \quad H \quad < \quad H_{c1}$ and $H \quad > \quad H_{c2}$, followed by a Mott insulating state above the saturation field $H_{sat}$. Note, that the critical fields $H_{c1,2}$ and $H_{sat}$ are shifted compared to those of pure DTN. In this talk, we report on measurements of the magnetization and specific heat at very low temperatures between 50 mK and 3 K in high magnetic fields up to 14 T on an 8{\%} Br-doped single crystal DTN. We compare our data with the local gap model, which reduces the low-temperature and low-field behavior to those of an ensemble of individual three level systems with local magnetization $M_{S}$ = 0, $\pm $1 and a finite energy gap for $H$ = 0.