Dear Ahmad Gholizadeh,

could you show the supplemental bode plots[1], also?

1. If possible, show, please, bode plots for the samples having a coercive field.

Dear Ioannis Samaras,

Attached is Nyquist diagram and Bode plots of the six samples.

Thank you in advance,

Dear Ahmad Gholizadeh !

You have performed the measurements at what temperature ... the shape of the curve is usually related to the measurement temperature.

Dear Oreci Escobar Da Silva,

All measurements have been done at room temperature. By the way, the experiments have been repeated twice.

But my problem is that the Nyquist diagram for the samples with zero coercive field are rotating counter-clockwise, while for the rest of the samples there is a clockwise rotation.

Thank you in advance,

Dear Oreci Escobar Da Silva,

I have downloaded some papers related to my work that can help to explain this phenomenon. According to the reported results, as you recommended, the shape of the curve is usually related to the measurement temperature.

https://www.researchgate.net/publication/257595853_Semiconductor_to_Metallic_Phase_Transition_in_Nickel_Doped_Co05Ni_X_Fe05-X_Fe2O4

https://www.researchgate.net/publication/230960300_Semiconductor_to_metallic_transition_and_polaron_conduction_in_nanostructured_cobalt_ferrite

https://www.researchgate.net/publication/257595853_Semiconductor_to_Metallic_Phase_Transition_in_Nickel_Doped_Co05Ni_X_Fe05-X_Fe2O4

https://www.researchgate.net/publication/263000352_Decrease_of_Metal_to_Semiconducting_Phase_Transition_Temperature_with_Increase_of_Particle_Size_in_Nickel_Ferrite

Thank you

Dear Ahmad Gholizadeh, so, you might think, implicitly, as if, it could be, any (possible ?) case about a "coercive field driven of a semiconductor to metallic" conductivity transition? Then, for our better perceptive, maybe you could try to (re-)plot, please, all (coercive field) cases in a single (the same) plot(s)[1,2].

Also, what are the VDC polarization parameter(s) (and the other parameters) in your measurements ?

1. Replot, please, the Nyquist diagrams (upper diagrams in the file "All ZZZZ.bmp") using the "same XY-tics", as usual, to think in terms of some (possible) equiv. circuit models.

2. Also, if you want to show a supplemental diagram with the (unusual) axis: LogZr versus LogZi, e.g. a "Nyquist like" plot, then, it would help us, more.

Dear Ioannis Samaras,

Thank you for your valuable comments. The studied samples are five different substituted Copper-Zinc ferrite. I think I should separately measure dielectric properties of each samples with increase in temperature. Then I can result about conductivity transition. Please let me know about your suggestion in this case?

Since, the samples with zero coercive field show low complex Impedance, high dielectric and high conductivity with respect to other, So, I can not suggest a equivalent circuit model for these two samples.

By the way, now, I don't know Vdc polarization in our measurments.

Attached is Nyquist diagrams of all samples.

Dear Ahmed Gholizadeh,

Please verify the resisriviry of the copper zinc ferrie samples. Are you sure they have high resitiviy of the order of 10^7 to 10^9. Then only you will get any meaningful imedance data.

Moreover as for as my knowledge there are no semiconductor to metal transitions.

All the peculiarities exhibited in ferrites are due the presence of multiple valace ions in different valance states. Please verify before going to study their physical properties.

Dear Kota venkata Sivakumar,

The resistance values of the samples are in the range of 300-800 Megaohm.

Thank you

Dear Ahmad Gholizadeh,

for the main complex Impedance issues[1,2], in the two samples, having a near zero (sum total) coercive field, should be culpable some extended metallic inclusions (high, near DC, conductivity), that, in addition, should be magnetic[2] ("rotating" counter-clockwise).

1. Your quote#1: The samples having coercive field show ordinary Z''-Z' circle plot , but they with zero coercive field show plots as follow.

2. Your quote#2: But my problem is that the Nyquist diagram for the samples with zero coercive field are rotating counter-clockwise, while for the rest of the samples there is a clockwise rotation.

Also, the two samples (indicated up), are above the (conductivity[1]) percolation limit[2,3] class, in contrast to the other samples (having a common[4.5] impedance), that are below the percolation limit.

1. a) https://www.researchgate.net/post/What_is_the_percolation_threshold_in_case_of_polymer_matrix_composite_and_what_is_its_significance

b) https://en.wikipedia.org/wiki/Percolation_threshold

2. Magnetic properties and anisotropic coercivity in nanogranular films of Co/Al2O3 above the percolation limit http://iopscience.iop.org/article/10.1088/0022-3727/47/34/345002/pdf

3. Percolation Magnetism in Ferroelectric Nanoparticles Article Percolation Magnetism in Ferroelectric Nanoparticles

4. Transport properties in iron–iron oxide film near percolation threshold Article Transport properties in iron–iron oxide film near percolatio...

5. Grain Boundary Wetting in Polycrystals... Article Grain Boundary Wetting in Polycrystals: 2. Percolation Model...

Dear Ioannis Samaras,

Thank you for your valuable suggestions.

Attached is AC-Conductivity plot of the samples. According to your suggestion, higher values of AC- Conductivity of two samples having zero coercive field is resulted from this phenomena. The slope in the range of smaller than 10kHz is negative. Can it related to the transition from long-range (smaller than 10kHz) to short-range (higher than 10kHz)?

The higher values of (DC and AC) conductivity S of these two samples, having a near zero (sum total) coercive field, can be, approximately, modelled as (S=) S1+S2 , where S1 a common class conductivity type, appearing in all your samples, and S2 is due to the extended metallic (and magnetic) inclusions. This (parallel, partial) conductivity S2 decreases[1] over the frequency and it prevails[2] (S=S1+S2 ~ 0+S2) up to[2] about 10kHz. On the contrary, at the higher values of frequencies the conductivity S (S=S1+S2 ~ S1+0) results in a common conductivity type (S~S1) , as all the (other) samples.

1. due to the magnetic conductivity type of the extended metallic inclusions.

2. Low pass filter, a material based low pass filter in a lumped (element model) component. Proposal applications are hybrid ICs, wires in PCBs etc.