Exchange bias in bulk Ni-Mn-In-based Heusler alloys

The crystal structure and exchange bias of the bulk Heusler alloys Ni50Mn50-xInx with 14.5 <= x <= 15.2 have been investigated using X-ray diffraction and magnetization measurements, respectively. Magnetic measurements were performed with SQUID magnetometry after samples were zero-field cooled and field cooled (FC) in positive magnetic fields upto H = 50 kOe, from a temperature T = 380 K. Three temperatures of the phase transitions, T-1 < T-M < T-C, and a shift of the FC (50 kOe) magnetic hysteresis loops up to 120 Oe at 5 K have been detected for all samples. The exchange bias field(HE) was almost constant for intermediate In concentrations 14.8<15.2, and sharply decreased to about 20 Oe on the borders of this concentration interval (x <= 14.5; 15.2 <= x). The changes of H-E have been related to changes in the ratio of T-1 to T-M: the overlapping of transitions at T-1 and T-M (for x = 14.8, and 15.2) results in a decrease in H-E. (C) 2008 Elsevier B.V. All rights reserved.