Experimental and Theoretical Investigations of Fe-Doped Hexagonal MnNiGe

We report a comprehensive investigation of MnNi0.7Fe0.3Ge Heusler alloy to explore its magnetic, caloric, and electrical transport properties. The alloy undergoes a ferromagnetic transition across TC∼212 K and a weak-antiferromagnetic transition across Tt∼180 K followed by a spin-glass transition below Tf∼51.85 K. A second-order phase transition across TCwith mixed short and long-range magnetic interactions is confirmed through the critical exponent study and universal scaling of magnetic entropy and magnetoresistance. A weak first-order phase transition is evident across Ttfrom magnetization and specific heat data. The frequency dependent cusp in χAC(T) along with the absence of a clear magnetic transition in specific heat C(T) and resistivity ρ(T) establish the spin glass behavior below Tf. Mixed ferromagnetic and antiferromagnetic interactions with dominant ferromagnetic coupling, as revealed by density functional calculations, are experimentally evident from the large positive Weiss temperature, magnetic saturation, and negative magnetic-entropy and magnetoresistance. © 2022 American Chemical Society. All rights reserved.CSR-IC-256/2017-18/1337; Department of Physics, Harvard University; Council of Scientific and Industrial Research, India, CSIR: 09/926(0011)2K18, DST/INT/RFBR/IDIR/P-01/2016; Ministry of Education and Science of the Russian Federation, Minobrnauka: AAAA-A18-118020190098-5; Indian Institute of Technology Bombay, IITB; Russian Science Foundation, RSF: 22-42-02021; UGC-DAE Consortium for Scientific Research, University Grants Commission, UGC-DAE CSR; Industrial Research and Consultancy Centre, IRCCS.S.S., A.K.P., and K.G.S. thank IRCC and the Department of Physics, IIT Bombay, for X-ray diffraction and magnetization facilities. S.S.S. acknowledges UGC-DAE CSR, Indore, for financial support under the Collaborative Research Scheme (CSR-IC-256/2017-18/1337). V.G. acknowledges UGC-DAE CSR, Indore, for the support. A.K.M. thanks CSIR India, for SRF [File No.: 09/926(0011)2K18]. K.G.S. acknowledges financial support through Indo-Russian project: DST/INT/RFBR/IDIR/P-01/2016. The theoretical studies are supported by the Russian Science Foundation (Project No. 22-42-02021) for the electronic structure calculations and Ministry of Science and Higher Education of the Russian Federation for the exchange parameters calculations (theme "Electron" No. AAAA-A18-118020190098-5).S.S.S., A.K.P., and K.G.S. thank IRCC and the Department of Physics, IIT Bombay, for X-ray diffraction and magnetization facilities. S.S.S. acknowledges UGC-DAE CSR, Indore, for financial support under the Collaborative Research Scheme (CSR-IC-256/2017-18/1337). V.G. acknowledges UGC-DAE CSR, Indore, for the support. A.K.M. thanks CSIR, India, for SRF [File No.: 09/926(0011)2K18]. K.G.S. acknowledges financial support through Indo-Russian project: DST/INT/RFBR/IDIR/P-01/2016. The theoretical studies are supported by the Russian Science Foundation (Project No. 22-42-02021) for the electronic structure calculations and Ministry of Science and Higher Education of the Russian Federation for the exchange parameters calculations (theme “Electron” No. AAAA-A18-118020190098-5)