Bistability in magnetic resonance

Two types of EPR (electron paramagnetic resonance) detectable bistability have been detected during recent years. The first is related to the EPR spectrometer itself and not to the sample. The physical cause of the phenomenon is the non-linear behaviour of the sample to cavity coupling [26]. The width of the hysteresis loop was found to vary with the filling factor of the cavity. This type was detected by Giordano et al. [26] during studies on polypyrrole radical. 

The second type of bistability is intrinsic to the conduction electron spins. Under saturation conditions, Overhauser effect is the primary condition for the observation of bistability. Under such a condition, the effective magnetic field, and hence the nuclear field takes two stable steady-state values for a given value of the external magnetic 

Conduction electrons in gallium oxide 3-Ga203 exhibit bistability detectable by EPR at X band (V = 8.4 GHz BO, 340 mT) and temperatures higher than 100 K, but the effect is also observable at room temperature. 

Since electro-kinetic systems can be maintained in the far-from-equilibrium region to any desired extent by controlling the variables, they constitute a very good system for the study of dynamic instability from experimental angle. A brief discussion of bistability and oscillations in electro-kinetic phenomena from an experimental point of view is given below. 

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