I have a semiconducting material that is diamagnetic in nature. On doping with magnetic ions, it shows paramagnetic behaviour. Further on substituting a non-magnetic ion into the system, it shows a small hysteresis curve. Magnetoresistance study of the sample shows negative behaviour at lower values of temperature and positive behaviour as temperature increases. What does this transition indicate?
On doping magnetic ion in the sample, magnetic ordering(spin orentation in the direction of magnetic field) will increase by applying magnetic field. At this situation, system resistance decrease (negative behavior with field) due to favorable condition in the direction of field. But this phenomena occured at low temperature and low magnetic field (means critical values).
Satyendra Singh Thank you for your reply. And with increasing temperature, there is a transition to positive behaviour, which means resistance is increasing. How does that come about?
As you increase temperature ( there is a change in magnetisation like ferro to para), spin fluctuation increase and random orientation of spin increase resistance.
But in case of low temperature, spin orients in a certain direction due to which resistance decrease.
Satyendra Singh Can we co-relate this result with VSM (M-H) results? Because in my case, 1st sample shows paramagnetic behaviour on doping with magnetic ion and the magnetoresistance behaviour is as discussed above i.e negative behaviour at low temperatures and transition to positive at high temperature.
2nd sample shows small ferromagnetism from the M-H curve but the magnetoresistance behaviour is the same as for the 1st sample.
Relative to Ferro negative MR should be low in Para ideally, but it can depend on the spin orientation with magnetic field and temperature. If spin orientation is more, it will be more. Check with the area of the loop and corecivity.
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