Effects of Cobalt on the Crystalline Structures of the Ni-Mn-In Giant Magnetocaloric Heusler Alloys

Conference · Mon Jun 01 04:00:00 EDT 2015 · Springer Proceedings in Energy

DOI:https://doi.org/10.1007/978-3-319-16901-9_62· OSTI ID:1485317

Madiligama, A ^[1]; Ari-Gur, Pnina ^[1]; Shavrov, V ^[2]; Koledov, V ^[2]; Ren, Yang ^[3]; Calder, Stuart A. ^[4]; Kayani, A ^[1]

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1. Western Michigan University, Kalamazoo
2. Kotelnikov Institute of Radio-engineering and Electronics of RAS,
3. Argonne National Laboratory (ANL), Advanced Photon Source (APS)
4. ORNL

The giant inverse magnetocaloric effect driven by a merged magneto-structural transformations in Ni-Mn-In-Co Heusler alloys, makes them highly promising as solid state refrigerants near room temperature. Knowledge of the crystallographic behavior of these alloys at a broad temperature range is critical to the understanding of the giant magnetocaloric effect. In this study, three Ni-Mn-In-Co alloys were investigated by neutron and synchrotron diffraction techniques. The chemical compositions of the alloys, determined by the Rutherford Backscattering Spectrometry (RBS) technique, were Ni₄₁Mn₃₉In₁₂Co₈, Ni₄₈Mn₃₄In₁₂Co₆ and Ni₅₂Mn₂₅In₁₆Co₇. The austenitic (A) phase of all three alloys was cubic L2₁ (Fm$$ \overline{3}\ $$m). Martensitic (M) phase of the Ni₄₁Mn₃₉In₁₂Co₈ alloy was a mix of 8M and 6M modulated monoclinic structures, while the other two alloys had a M composed of a mix of ₇M and ₅M modulated monoclinic structures. All modulated structures belong to the P 1 2/m 1 space group. Site occupancy refinements of the A phases of all three alloys, revealed that almost all the Co atoms (~97%) occupy the regular Ni (8c) sites. In the studied temperature range (50–250 K) of the M phase of the Ni₄₁Mn₃₉In₁₂Co₈ alloy has very low magnetization. Also, no antiferromagnetic ordring was observed in the neutron diffraction refinement of the M phase. Therefore by eliminating the possibilities of ferromagnetism and antiferromagnetism, it is concluded that the M phase of the Ni₄₁Mn₃₉In₁₂Co₈ alloy is spin glass.

• Research Organization: Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
• DOE Contract Number: AC05-00OR22725
• OSTI ID: 1485317
• Conference Information: Journal Name: Springer Proceedings in Energy Journal Issue: none Journal Volume: 4
• Country of Publication: United States
• Language: English