Influences of Si Substitution on Existence, Structural and Magnetic Properties of the CoMnGe Phase Investigated in a Co-Mn-Ge-Si Thin-Film Materials Library.

Materials exhibiting a giant magnetocaloric effect (GMCE) need to be finely tuned with respect to their magnetic and structural properties, specifically their respective transition temperatures. Co-Mn-Ge and Co-Mn-Ge-Si thin-film materials libraries (MLs) were fabricated and characterized to determine the composition range in which the CoMnGe phase is stable and analyze selected single-phase measurement regions. Phase analysis was performed on these MLs and refined in regard to the CoMnGe single-phase region by synchrotron diffraction experiments. A comparison of the MLs revealed that the CoMnGe (HT) single-phase region gets smaller with the addition of Si and exists for 26.5 at. % < Co < 29.5 at. %, 34 at. % < Mn < 37 at. %, Ge ∼ 35 at. %, and Si ∼ 1.5 at. % in the quaternary ML. The investigation of magnetic and structural transition properties in this region revealed hard-magnetic behavior with Curie temperatures (