Large exchange bias in magnetic shape memory alloys by tuning magnetic ground state and magnetic-field history

The exchange bias is of technological significance in magnetic recording and spintronic devices. Pursuing a large bias field is a long-term goal for the research field of magnetic shape memory alloys. In this work, a large bias field of 0.53 T is achieved in the Ni₅₀Mn₃₄In_16-xFe_x (x = 1, 3, 5) system by tuning the magnetic ground state (determined by the composition x) and the magnetic-field history (determined by the magnetic field H_FC during field cooling and the maximum field H_Max during isothermal magnetization). The maximum volume fraction of the interfaces between the ferromagnetic clusters and antiferromagnetic matrix and the strong interfacial interaction are achieved by tuning the magnetic ground state and the magnetic-field history, which results in strong magnetic unidirectional anisotropy and the large exchange bias. Moreover, two guidelines were proposed to obtain the large bias field. Firstly, the composition with a magnetic ground state consisting of the dilute spin glass and the strong antiferromagnetic matrix is preferred to obtain a large bias field; secondly, tuning the magnetic-field history by enhancing H_FC and reducing H_Max is beneficial to achieving large exchange bias. Our work provides an effective way for designing magnetically inhomogeneous compounds with large exchange bias.