SKM 2023 – wissenschaftliches Programm

Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe

MA: Fachverband Magnetismus

MA 23: Poster Magnetism I

MA 23.17: Poster

Dienstag, 28. März 2023, 17:00–19:00, P1

Probing the nature of first-order magnetostructural transitions as responsible for magnetocaloric effects: A case study for In-based Heusler alloys — •Chris Taake¹, Tapas Samanta¹, and Luana Caron^{1, 2} — ¹Faculty of Physics, Bielefeld University, PO Box 100131, D-33501 Bielefeld, Germany — ²Helmholtz-Zentrum Berlin für Materialien und Energie, Berlin 12489, Germany

The subtle nature of magnetostructural transitions (MST) and associated magnetocaloric effects (MCE) in B-substituted In-based Heusler alloys Ni₅₀Mn_34.8In_15.2−xB_x (x=1, 2 and 3) have been studied. Boron substitution acts as a positive chemical pressure and shifts the martensitic phase transition temperature (T_M) towards higher temperature with increasing B concentration. Magnetic field sensitivity of T_M as well as thermal hysteresis decrease with increasing B substitution. Because of the compensation effect between the loss of field sensitivity and decreased thermal hysteresis, a similar reversible MCE can be expected for all studied compositions. However, a much better reversible isothermal entropy change (ΔS) has been observed for x=1, which reaches a value of +20.8 J/kg K for ΔH=5 T. The observed behavior clearly indicates that the nature of the MST responsible for the MCE is changing with composition. To understand the nature of the MST in depth, the behavior of the local magnetic field exponent, n (ΔS ∝ Hⁿ), has been examined for all the compositions. Interestingly, a much larger n^max (=10.35, where n >2 is the indication of a first-order phase transition) has been detected for x=1 when compared to other compositions which are less field sensitive (n^max=3.66, x=3).