2019/04/25 by Riaz Hussain, Francesco Cugini, Hussain, R. +23
Materials Science · #FOS: Physical sciences #Magnetic Properties of Alloys #Magnetic and transport properties of perovskites and related materials #Shape Memory Alloy Transformations #Strongly Correlated Electrons (cond-mat.str-el)
paper · pdf · doi:10.48550/arxiv.1904.11629
openalex publication_date 2019/04/25 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We report on a study on a representative set of Fe2P-based MnFePSi\nsamples by means of 55Mn NMR in both zero and applied magnetic field. The\nfirst-order nature of the magnetic transition is demonstrated by truncated\norder parameter curves with a large value of the local ordered moment at the\nCurie point, even at compositions where the transition appears second order\nfrom magnetic measurements. No weak ferromagnetic order could be detected at\nSi-poor compositions showing the kinetic arrest phenomenon, but rather the\nphase separation of fully ferromagnetic domains from volume fractions where Mn\nspins are fluctuating. The more pronounced decrease of the ordered moment at\nthe 3f sites on approaching TC, characteristic of the mixed magnetism of\nthese materials, is demonstrated to be driven by a vanishing spin density\nrather than enhanced spin fluctuations at the 3f site. An upper limit of\n0.03~\μB is set for the fluctuating Mn moment at the 3f site by the\ndirect detection of a 55Mn NMR resonance peak in the Mn-rich samples above\nTC, showing nearly temperature-independent frequency shifts. A sharper\nsecondary peak observed at the same compositions reveals however the\ndisproportionation of a significant 3f-Mn fraction with negligible hyperfine\ncouplings, which retains its diamagnetic character across the transition, down\nto the lowest available temperatures. Such a diamagnetic fraction qualitatively\naccounts for the reduced average 3f moment previously reported at large Mn\nconcentrations.\n