Structural And Magnetic Properties In Off-Stoichiometric MnNiGe Based Thin Film And Bulk Compounds

The crystal structure, magnetic properties and magnetocaloric effect in NiMnGe based thin film and bulk compounds are studied by room temperature XRD and magnetization measurements.The bulk compounds Ni$_{\mathrm{0.895}}$Cr$_{\mathrm{0.105}}$MnGe$_{\mathrm{1.05\thinspace }}$and Ni$_{\mathrm{0.93}}$Cr$_{\mathrm{0.07}}$MnGe$_{\mathrm{1.05\thinspace }}$were prepared by arc melting process. Thin film was obtained from Ni$_{\mathrm{0.895}}$Cr$_{\mathrm{0.105}}$MnGe$_{\mathrm{1.05\thinspace }}$target using Pulsed Laser Deposition technique on MgO substrate. Both bulk and thin film crystalizes into hexagonal structure. For bulk Ni$_{\mathrm{0.895}}$Cr$_{\mathrm{0.105}}$MnGe$_{\mathrm{1.05\thinspace }}$a first order magnetostructural transition from antiferromagnetic orthorhombic to ferromagnetic hexagonal structure was observed near transition temperature 134 K followed by the second order transition (SOT) from ferromagnetic to paramagnetic near Curie temperature T$_{\mathrm{c}} \quad =$ 204 K. In case of thin film only the presence of SOT was observed near T$_{\mathrm{c}}$. For Ni$_{\mathrm{0.93}}$Cr$_{\mathrm{0.07}}$MnGe$_{\mathrm{1.05,}} \quad \Delta $T $=$ 0.65K near T$_{\mathrm{c\thinspace }}=$ 209 K for $\Delta $H $=$ 1.8 T was observed. This work was supported by the U.S. DOE Award No. DE-FG02-06ER46291 {\&} DE-FG02-13ER46946. Authors at Moscow State Univ. acknowledge Russian Foundation for Basic Research (Grant No. 15-02-01976). A. Sokolov acknowledges support from NSF DMR-1310542 grant.