Transcript NJU09071
Structural, magnetic and electrical transport properties in Heusler-type Ni
50-x
Fe
x
Mn
25
Ga
25
melt-spun ribbons and Fe-Mn-Ga
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 Ni 50-x Fe x Mn 25 Ga 25 melt-spun ribbons based on Ni 2 MnGa 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.
x=25 x=30 x=40 Fe 50 Mn 17 Ga 33 Fe 2 MnGa Fig. 3 X-ray diffraction patterns of Fe 2 MnGa and Fe 50 Mn 17 Ga 33 melt spun ribbons (L2 1 structure). The lattice constant of Fe 50 Mn 17 Ga 33 is 5.874 Ǻ , which is larger than that of Fe 2 MnGa because of the larger atomic radius of Ga. 30 45 2 60 75 90 30 45 2 60 75 90 Fig. 1 X-ray diffraction patterns of Ni 50-x Fe x Mn 25 Ga 25 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 Ni 2 MnGa to 5.832Ǻ in Fe 2 MnGa.
380 360 340 320 300 280 260 240 0 10 20 30 40 50 100 95 90 85 80 75 70 65 60 55 0 10 20 30 40 x x 50 Fig. 2 Curie temperature and saturated magnetization as a function of Fe content for Ni 50-x Fe x Mn 25 Ga 25 melt-spun ribbons. Both decrease with Fe increasing due to the antiferromagnetic coupling between Fe-Mn atoms.
Conclusion:
40 30 20 10 0 0 50 100 150
T(K)
200
Fe 50 Mn 17 Ga 33 Fe 2 MnGa
250 80 60 40 20 0 -20 -40 -60 300 -10000
Fig. 4 FC/ZFC of Fe 2 MnGa and Fe 50 Mn 17 Ga 33 ribbons with the applied field of 100Oe. The magnetic behaviors are similar to that of spin glass system.
In Ni 50-x Fe x Mn 25 Ga 25 melt-spun ribbons: The addition of Fe does not change the L2 1 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.
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0 50 100
Fe 50 Mn 17 Ga 33 Fe 2 MnGa
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T(K)
200 250 300 0
Fe 50 Mn 17 Ga 33 Fe 2 MnGa
10000 20000 30000 40000 50000
H(Oe) Fig.5 Magnetization curves of Fe 2 MnGa and Fe 50 Mn 17 Ga 33 ribbons at 5K. The Curie temperature and saturated magnetization increase with the decreasing content of Mn. Fig. 6 Temperature dependences of Fe 2 MnGa and Fe 50 Mn 17 Ga 33 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.