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

Salomon, S. and Wöhrle, F. and Hübner, P. and Decker, P. and Ludwig, Al.

Volume: 21 Pages: 675-684
DOI: 10.1021/acscombsci.9b00107
Published: 2019

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 (Tc) between 261 and 274 K and large hysteresis widths with values >100 K for the structural transition. A low Co content was necessary to achieve an overlap of Tc and structural transition temperatures, leading to the most favorable properties for a GMCE to be found in Co26.5Mn37Ge35Si1.5. © 2019 American Chemical Society.

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