Introduction:

1. Structural, magnetic and electrical transport properties in Heusler-type Ni50-xFexMn25Ga25 and Fe-Mn-Ga melt-spun ribbons L. Zhao, Shuyun Yu and Shishen Yan School of Physics, Shandong University, Jinan 250100, P.R.China • Introduction: • Heusler alloys have attracted considerable research attention in recent years due to the promising applying value of magnetoelectonic and spintronic devices. • Quaternary additions of transition elements such as Fe are reported to have a big influence on the structural and magnetic properties of Heusler alloys. • In this work, the quaternary Heusler-type Ni50-xFexMn25Ga25 melt-spun ribbons based on Ni2MnGa with an intended substitution of Ni by Fe were characterized for their structural and magnetic properties. • The magnetic and electrical transport properties of ternary Fe-Mn-Ga melt-spun ribbons were also investigated. • Methods: • The crystalline NiFeMnGa and FeMnGa alloys were prepared by arc melting of high-purity metals under argon atmosphere. • The ribbons were made from the ingots by melt spinning method. Fig. 3 X-ray diffraction patterns of Fe2MnGa and Fe50Mn17Ga33 melt-spun ribbons (L21 structure). The lattice constant of Fe50Mn17Ga33 is 5.874 Ǻ , which is larger than that of Fe2MnGabecause of the larger atomic radius of Ga. Fig. 1 X-ray diffraction patterns of Ni50-xFexMn25Ga25 melt-spun ribbons. The L21 structure is observed in the whole composition range. The lattice constant increases slowly with the addition of Fe, from 5.824Ǻ in Ni2MnGato 5.832Ǻ in Fe2MnGa. Fig. 4 FC/ZFC of Fe2MnGa and Fe50Mn17Ga33 ribbons with the applied field of 100Oe. The magnetic behaviors are similar to that of spin glass system. Fig.5 Magnetization curves of Fe2MnGa and Fe50Mn17Ga33 ribbons at 5K. The Curie temperature and saturated magnetization increase with the decreasing content of Mn. Fig. 2 Curie temperature and saturated magnetization as a function of Fe content for Ni50-xFexMn25Ga25 melt-spun ribbons. Both decrease with Fe increasing due to the antiferromagnetic coupling between Fe-Mn atoms. Fig. 6 Temperature dependences of Fe2MnGa and Fe50Mn17Ga33 melt-spun ribbons. The electrical transport behaviors at low temperature are similar to Kondo effect, while at high temperature, a change from metal to semiconductor-like behavior occurs. • Conclusion: • In Ni50-xFexMn25Ga25 melt-spun ribbons: • The addition of Fe does not change the L21 structure. • The Curie temperature and saturated magnetization decrease linearly with the incerasing of Fe due to the antiferromagnetic interaction between Fe and Mn. In Fe-Mn-Ga system: The magnetic behavior is similar to that of spin glass system and a minimum in the resistivity-temperature curve has been found. More detailed investigations are needed to get a clear physical mechanism. Corresponding author: lezhao2007@gmail.com