Phase transitions, magnetotransport and magnetocaloric effects in a new family of quaternary Ni-Mn-In-Z heusler alloys

The magnetic, magnetotransport, and magnetocaloric properties near compound phase transitions in Ni 50Mn 35In 14Z (Z=In, Ge, Al), and Ni 48Co 2Mn 35In 15 Heusler alloys have been studied using VSM and SQUID magnetometers (at magnetic fields (H) up to 5 T), four-probe method (at H = 0.005-1.5 T), and an adiabatic magnetocalorimeter (for H changes up to δH = 1.8 T), respectively. The martensitic transformation (MT) is accompanied by large magnetoresistance (up to 70%), a significant change in resistivity (up to 200%), and a sign reversal of the ordinary Hall effect coefficient, all related to a strong change in the electronic spectrum at the MT. The field dependences of the Hall resistance are complex in the vicinity of the MT, indicating a change in the relative concentrations of the austenite and martensite phases at strong fields. Negative and positive changes in adiabatic temperatures of about -2 K and +2 K have been observed in the vicinity of MT and Curie temperatures, respectively, for δH = 1.8 T. Copyright © 2012 American Scientific Publishers All rights reserved