On the correct estimation of the magnetic entropy change across the magneto-structural transition from the Maxwell relation: Study of MnCoGeBX alloy ribbons


Quintana-Nedelcos A., Sanchez Llamazares J. L. , Sanchez-Valdes C. F. , Alvarez Alonso P., Gorria P., Shamba P., ...More

JOURNAL OF ALLOYS AND COMPOUNDS, vol.694, pp.1189-1195, 2017 (Journal Indexed in SCI) identifier

  • Publication Type: Article / Article
  • Volume: 694
  • Publication Date: 2017
  • Doi Number: 10.1016/j.jallcom.2016.10.116
  • Title of Journal : JOURNAL OF ALLOYS AND COMPOUNDS
  • Page Numbers: pp.1189-1195

Abstract

An accurate calculation of the different magnetocaloric-related magnitudes derived from the temperature dependence of the magnetic entropy change in materials exhibiting first-order magnetocaloric effect is imperative to correctly estimate the true potential of a specific material for refrigeration purposes. In this contribution, we present a meticulous study of two different thermal procedures to measure the set of isothermal magnetization curves from which the total field induced magnetic entropy change, Delta S-T, is calculated using the adequate Maxwell relation. If the accurate determination of Delta S-T for any temperature is pursued the thermal and magnetic history of the materials must be taken into account, and then, the unidirectional measurement of reversible isothermal magnetization curves after a thermal cycle is required. The analysis was conducted on MnCoGeB0.01 alloy ribbons that show a giant Delta S-T at the coupled magneto-structural transition, from a ferromagnetic (TiNiSi-type) phase to a paramagnetic (NiIn2-type) one, owing to the concomitant abrupt magnetization change. We suggest that the conclusions reached can be applicable to any other system displaying magnetocaloric effect originated at a first order phase transition. (C) 2016 Elsevier B.V. All rights reserved.