Evolution of noncollinear magnetism in magnetocaloric MnPtGa

Joya A. Cooley, Joshua D. Bocarsly, Emily C. Schueller, Emily E. Levin, Efrain E. Rodriguez, Ashfia Huq, Saul H. Lapidus, Stephen D. Wilson, and Ram Seshadri
Phys. Rev. Materials 4, 044405 – Published 13 April 2020
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Abstract

MnPtGa crystallizes in the hexagonal Ni2In structure type in space group P63/mmc and has been reported to display a ferromagnetic Curie temperature near 220K. Here we find a transition near TC=236 K to a ferromagnetic state, albeit with a reduced moment from what is expected for collinear ordering. The peak magnetocaloric entropy change was determined to be ΔSM=1.9Jkg1K1 for an applied magnetic field of H=5T at the ferromagnetic ordering temperature. Magnetostructural coupling manifests as a change in the slope of the thermal expansion coefficients of the c lattice parameter near TC, with a negative spontaneous volume magnetostriction; ω=300 ppm at 190K. Neutron powder diffraction studies of the magnetic ground state reveal an evolution in complexity as temperature decreases: from a ferromagnet, to a canted antiferromagnet, to the eventual formation of a spin-density-wave state at low temperatures.

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  • Received 6 July 2019
  • Revised 18 February 2020
  • Accepted 17 March 2020

DOI:https://doi.org/10.1103/PhysRevMaterials.4.044405

©2020 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Joya A. Cooley1,*, Joshua D. Bocarsly1,2, Emily C. Schueller1,2, Emily E. Levin1,2, Efrain E. Rodriguez3, Ashfia Huq4, Saul H. Lapidus5, Stephen D. Wilson2, and Ram Seshadri1,2,6

  • 1Materials Research Laboratory, University of California, Santa Barbara, Santa Barbara, California 93106, USA
  • 2Materials Department, University of California, Santa Barbara, Santa Barbara, California 93106, USA
  • 3Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742, USA
  • 4Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
  • 5X-ray Sciences Division, Argonne National Laboratory, Lemont, Illinois 60439, USA
  • 6Department of Chemistry and Biochemistry, University of California, Santa Barbara, Santa Barbara, California 93106, USA

  • *jacooley@mrl.ucsb.edu

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Vol. 4, Iss. 4 — April 2020

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