In general if we can produce a good quality magnetic semiconducting material (Like Nanorods, Nanoparticles or a Thin film) by doping TM(Mn, Co, Ni) in a semiconducting host(ZnO, TiO2, GaN) system which shows intrinsic origin of the room temperature ferromagnetism (RT FM), it can work as a source of spin polarized carriers. I have synthesized Co doped ZnO thin film by co-sputtering technique and Co doped ZnO nanorods by chemical synthesis, RT FM have been observed. Now I want to study about the behavior of spin polarized carriers on these systems. So what possible measurements can be arranged for this purpose. Please write your views and comments on this issue.
Dera Werner..
Thank you for your suggestion. Here, I have tried too make the question specific to the kind of work I am related with. Basically I am working magnetic semiconducting materials, like TM doped ZnO films or nanostructures. So I want to study about the behavior of spin polarized carriers on these systems. So what possible measurements can be arranged for this purpose?
You could try muon spin rotation (muSR), which has been used to look at both dilute and stoichiometric magnetic semiconductors, but be prepared to find yourself embroiled in passionate disputes over interpretation of the data. I am not aware of any muSR results in doped ZnO, so it would be fun to have a look. See http://musr.ca
DMS based spintronic device are fascinating area in-spite of experimental difficulty. You have to be clear why you want to study the spin polarization of your sample. If your material shows good FM, try to fabricate FM/I/FM based junction and study the magnetoresistance of your sample. Use simple julliere formula to evaluate the spin polarisation of your material. It helps to certain extent. Theoretical results predicts 42-47% for cobalt.
For further understanding check the following papers
Phys Rev B 79 (2009) 165208
Phys Rev B 80 (2009) 245207
Nat Mater. 5 (2006) 298
One way of detecting spin polarisation is to observe a drop in resistance below the Currie Temperature of the ferromagnetic semiconductor.
Please refer to these two papers for a detailed discussion on the the above mentioned procedure and also for a simplistic formula of finding the efficiency of spin polarisation.
A. Pal et al, Adv. Mat., 2103.
T. S. Santos et al, PRL, 2008.
DMS material, especially cobalt doped ZnO has Curie temperature close to room temperature (280 K and above), so there will not be an abrupt drop in resistance below this temperature. I hope your observation can be used for materials possessing Curie temperature at very low temperature region. Is it so?
Thanks to all the colleagues for the valuable suggestions. I had read about the idea of magnetotransport measurement to study the spin polarization, specially by forming a MTJ. I will try that. But if I want to study a thin film at the first stage before forming the MTJ, is there any way to have idea on spin polarization? Because sometimes MTJ formation itself have some limitations depending on the fabrication setup's quality. Another thing is that, what should I do for the solid/ powder sample like rods/wires, particles to study the spin polarization behavior? Till now I have observed the Curie temperature above room temperature (300-500K) for the Co/Ni doped ZnO systems. So, as asked by Mr. Sridharan, for this kind of cases can the observance of resistance characteristics below the Curie temp provide good information in detecting the spin polarization?
Dear Jess Sir,
I appreaciate that muon spin rotation (muSR) might provide some good information about the sample properties related to spin polarization. I am too not aware of any muSR results in doped ZnO systems. But the main problem is that how do I range such measurement, its not available at near about my place of work. Also, may be it will be too costly to arrange for such measurement from here.
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