The magnetic entropy changes in Pb doped Ni-Mn-Cu-Ga alloys

Krzysztof Sielicki , Justyna Zygmuntowicz , Rafał Wróblewski , Marcin Leonowicz

Abstract

Effect of Pb addition on magnetocaloric properties of Ni50Mn18,75Cu6,25-aPbaGa25 (a = 1, 2, 3, 4, 5) alloys was investigated experimentally. The magnetic measurements conducted at low field of 4 kA/m showed that addition of Pb led to separation of the both transformation temperatures and significantly shifted the structural transition effect towards lower temperatures as well as increased the Curie temperature. The analysis of isothermal magnetic curves allowed for the calculation of magnetic entropy change (ΔSM). Although the peak values of |ΔSM| for alloys containing 4 and 5 at.% Pb, ~3 J/(kg*K) and ~1.5 J/(kg*K) respectively, are low they stretch over the structural transformation and Curie temperature, and are at least 30 K wide at half maximum height.