Magnetization reversal and negative volume thermal expansion in Fe doped Ca$_{2}$RuO$_{4}$*

We report structural, magnetic, transport and thermal properties of single-crystal Ca$_{2}$Ru$_{1-x}$Fe$_{x}$O$_{4}$ (0 $\le $ x $\le $ 0.2) as functions of pressure, magnetic field and temperature. The central findings of this work are a pronounced magnetization reversal and a negative thermal expansion that are induced by Fe doping. Our results including neutron diffraction data suggest that the magnetization reversal is primarily a result of different temperature dependences of two antiparallel, competing Ru and Fe sublattices and that the negative thermal expansion is achieved via magnetic and metal-insulator transitions. We will present and discuss our results with comparison drawn with relevant systems.