It is sometime told that if shift of the hysteresis loop both in the vertical and horizontal direction occurs then the exchange bias property observed is may be due to the minor loop effect. Is it so? If so then in which case it is correct? What exactly a minor loop means?
Hello Junmoni,
minor loops can indeed lead to measurements which seem to show an exchange bias, although in reality there is no EB. "Minor loop" means that the maximum external field values are chosen too low, so that the magnetization in the sample under examination is not completely switched. Normally one would assume that such a problem is visible at first glance - but as soon as there is a "step" in the hysteresis loop (e.g. here http://arxiv.org/ftp/cond-mat/papers/0508/0508635.pdf), this step can be believed to be a saturated state, and it is easily possible to do an experiment with too low maximum fields. Especially in nano-structures, this problem can occur quite easily, since often there are "steps" where the magneitzation is nearly completely switched, with only small parts of the structure not yet saturated, and these "steps" in the hysteresis loop can be nearly invisible especially in MOKE measurements (possibly leading to errouneously decreasing the maximum external field values).
BUT: It has been shown in Monte-Carlo simulations (e.g. http://kops.ub.uni-konstanz.de/bitstream/handle/urn:nbn:de:bsz:352-opus-92200/nowakscan1.pdf?sequence=1) that the exchange layer of an EB system can indeed cause a real upshift of the hysteresis loop, which has also often been recognized in SQUID measurements of EB systems. Thus, the combination of vertical and horizontal shift is absolutely not unusual for an EB system and no reason to believe that the apparent EB shift is based on a measurement error.
Hello Junmoni,
If you want to understand better what is a minor loop, I may recommend read a little bit about Preisach or L2P (Limiting loop proximity hysteresis model) [1] models. You may find the L2P model implemented in free software packages [2] and try some simulation.
[1] de Almeida, L.A.L.; Deep, G.S.; Lima, A.M.N.; Neff, H., "Limiting loop proximity hysteresis model," Magnetics, IEEE Transactions on , vol.39, no.1, pp.523,528, Jan 2003
doi: 10.1109/TMAG.2002.806344
[2] HysterSoft is a computer program for the simulation of hysteresis and related phenomena in hysteretic systems. It provides a user-friendly simulation framework, in which various mathematical models of hysteresis can be implemented numerically relatively easy. HysterSoft version 2.0 comes with the following models already implemented by default (these models are called predefined models): the backlash operator, the Bouc-Wen model, the Coleman-Hodgdon model, the stop (elastic-plastic) operator, the energetic model, the Jiles-Atherton model, the Langevin model, the limiting-loop proximity model, the Preisach model (including the cases in which the Preisach distribution is specified analytically or using discrete values defined on a mesh), and the rectangular-loop model. Users can also add additional models to the program by using predefined templates. These models are called user-defined models. http://www.eng.fsu.edu/ms/HysterSoft/#
Department of Electrical and Computer Engineering
Florida State University and Florida A&M University
- Badges
- Science topic
- Similar topics
- Correction