Structure and magnetic properties of Ni50−xCoxMn50−yAly (x = 5–9, y = 18–19) shape memory alloy ribbons

Abstract

Alloy ribbons of Ni 50−x Co x Mn 50−y Al y (x = 5, 6, 7, 8 and 9; y = 18 and 19) were fabricated by using melt-spinning method. By varying Co and Al concentrations, the formation of crystalline phases, structural transformations and magnetic phase transitions can be tuned as desired. With high Al and Co concentrations, only a ferromagnetic-paramagnetic (FM-PM) transition of the austenitic phase occurs in the range of 350–450 K. While there is an additional weak ferromagnetic- ferromagnetic (WFM-FM) transition corresponding to the martensitic-austenitic (M-A) structural transformation for the ribbons with low Al and Co concentrations. The M-A transformation temperature of the alloy ribbons can be obtained in the range of 150–360 K. An anomalous change in structure and magnetic properties was observed in the ribbon sample with Co and Al concentrations of 8 and 18 at%, respectively. The external magnetic field has a pronounced effect on the M-A transformation and tends to shift this process towards lower temperatures. • Structure and magnetic properties of Ni 50−x Co x Mn 50−y Al y rapidly solidified alloys. • Influence of Co and Al contents on structural transformation and magnetic transition. • Coexistence of different crystalline phases in Heusler magnetic shape memory alloys. • Tuning structural transformation and magnetic transition of Ni-Co-Mn-Al alloys. • Transformation of metamagnetic phase in Ni-Co-Mn-Al rapidly solidified alloys.