The Magnetic and Exchange Bias Properties of Phase Segregated Mn2-xFexNi1.6Ga0.4

Abstract

The exchange bias (EB) phenomenon, generally quantified by the shift of the hysteresis loop along the magnetic field axis, has been observed in several Mn-rich Heusler alloys [1, 2, 3]. The fundamental science that drives EB and its technological impact are both of great interest [4, 5]. The EB effect in Mn-rich Heusler alloys is primarily related to the coexisting ferromagnetic (FM) and antiferromagnetic (AFM) interactions. Interestingly, the Mn atoms are responsible for both the FM and AFM interactions in these materials. In the Heusler alloy Mn(2)NiGa, both FM and AFM interactions are present. However, the material does not exhibit any EB effect. Interestingly, a strong EB was observed in Ga-deficient/Ni-rich Mn(2)Ni(1.4)Ga(0.6), which demonstrated the importance of crystalline site occupancies of the Mn atoms in driving EB [6]. Here, we have performed an experimental study on the effect of Fe doping on the magnetic and EB properties of Mn(2-x)Fe(x)Ni(1.6)Ga(0.4) (0 ≤ x ≤ 0.35). The goal of the study was to explore the effect of Fe doping on the FM and AFM interactions in the system. The samples were fabricated by arc melting, drop-casting, and annealing techniques. X-ray diffraction measurements and the scanning electron microscopy images showed that the alloys were phase segregated with two different lower symmetry structures. For all values of x, EB was observed in the materials. An EB field of as large as ~4000 Oe and a coercive field of ~14 kOe were observed in the materials. The structural, magnetic, and EB properties of all the alloys in the Mn(2.x)Fe(x)Ni(1.6)Ga(0.4) system will be presented.