Combinatorial synthesis and high-throughput characterization of the thin film materials system Co-Mn-Ge: Composition, structure, and magnetic properties

Co- Mn-Ge is a system of interest for magnetocaloric applications as a solid state magnetic refrigerant. A thin him materials lihrary COVering a large fraction of the Co Mn Ge ternary composition space as fahricated hy sputter deposition. Alter deposition. it was annealed at 600 degrees C lor 3 h and cmenched subsequently. An energy-dispersive X-ray spectroscopy and X-ray diffraction-based cluster analysis revealed he regions oh existence or he CoMnGe and the Co(2)NinGe single phase (treas. Furthermore. high intensity diffraction peaks revealed the presence oh the hexagonal (Co. Mr)7Ge,, phase in a region that also featured the CoMnGe phase. In this region. a non-linear. symmetric. and hysteretic shin. of the (200) diffraction peak of the (Co. NlnI-Ge,, phase as observed by temperature-dependent X-ray diffraction for CotttMmtGe44. indicating a structural phase transition taking place hemeen 35 and 375 K upon heating and 325 and 300 K Upon cooling. This coincides with a magnetic transition near 325 K from the ferromagnetic to the paramagnetic state. I lowever. no Magnetostructural coupling was identined 111 the temperature range from 330 to 300 K upon coolillg. Magnetostriction and an undetected structural transition of the CoMnGe phase were ruled out as probable causes or the non-linear shifts. (C) 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim