for example i have got two M-H curves. can by just looking at curves we can say that its ferromagnetic or ferrimagentic in nature?
Some of my friends say they are able to distinguish such two cases by just a visual inspection, but until today they were unable to convincingly explain how do they do it. One thing, however, is sure: once you see a hysteresis loop (non-zero coercivity and non-zero remanence) then there must be a ferromagnetic interaction in the observed system. Bad news is: it doesn't mean it's the only one. In canted structures ("weak" ferromagnets) you may even observe hysteresis consisting of two loops, roughly speaking in I and III quarter of M-H plane, with surrounding of (0,0) point being unique. Diamagnets (but not superconductors), paramagnets and superparamagnets produce unique curve, almost linear and passing through (0,0), if the temperature is high enough. Ferrimagnets are probably best identified by their M(T) curves, changing sign at specific temperature, somewhere between 0 and Tc (TN?).
Ravindra solanki ................ Can we differentiate on basis of x-ray diffraction also?
Well, ordinary X-ray examination is indeed unable to 'see' anything magnetic. But using polarized radiation you may be able to investigate MCD (magnetic circular dichroism) signal. I'm not sure whether this technique distinguishes between various magnetic structures.
see: http://en.wikipedia.org/wiki/Magnetic_circular_dichroism
"Magnetic circular dichroism (MCD) is the differential absorption of left and right circularly polarized (LCP and RCP) light, induced in a sample by a strong magnetic field oriented parallel to the direction of light propagation. ..."
You may think that there are two different indexes of refraction for RCP and LCP light, caused by the presence of longitudinal magnetic field. This effect in optics is known under the name of "Faraday effect". In optics the result is that linearly polarized light changes its direction of polarization while passing through the magnetized sample (or just located in the external magnetic field) when absorption is negligible, or becomes elliptically polarized when absorption cannot be neglected. You may have heard about "dichroism" in its other, better known meaning: splitting of the incoming light ray into two components, namely ordinary ray and extraordinary ray - but this one is a different phenomenon, not related to magnetism.
Can any 1 further help me in analysis of dielectric constant ........... What i have got is capacitance value of the thin film ........... How to convert it into dielectric value?
You need to know the size of your thin film capacitor, i.e. its area and film thickness.
The calculation is easy, see the appropriate formula at
http://en.wikipedia.org/wiki/Capacitance
I calculate the relative permittivity of organic thin film i got 3 multipy by 10 power 3 result. which is impossible.. i take my experimental value of capacitance at room temperature which is 1.66 multiply by 10^-11 farad d=40micro meter A= 100nm(thickness of electrode/plate) multiply by 0.025m (width) and permittivity of free space.How i calculate the real value
"A" in the formula is *not* the thickness of an electrode but its area, while "d" is the distance between two plane-parallel electrodes. The formula is valid when the electric field between electrodes is uniform, meaning - among other things - that the space between electrodes is completely filled with material under investigation. Suppose you have lower electrode quite big, the material is placed on it (material thickness is "d") and covered (maybe not completely) with upper electrode. If this is the case, then the number "A" means the area of an upper electrode. When upper electrode is bigger than lateral size of the sample, then you have in fact two capacitors connected in parallel.
One more thing: at high frequencies, when (lateral) sizes are comparable with wavelength, the simple formula must fail. With dimensions you quote this may happen above, say, at least 10 GHz, so you are probably safe.
Any air column in such thin condenser will give quite wrong results.
Any body can explain the structure{(4,5-diphenyl-1H-imidazol-2yl) phenol} of an imidazole base organic semiconducting material with OH functional group attached.
My feeling is that due to their structure the hysteresis loop for ferrimagnetic material should be narrower than for ferromagnetic material.
@ Marek Wojciech Gutowski : As you have mentioned above that in case of ferrimagnetism MT will show negative sign in bet 0 and Tc. Can you please elaborate this point a bit more.Does canted AF structure shows negative magnetization?
Ooops. I have mixed ferrimagnets with antiferromagnets. Of course, ferrimagnets with both sublattices oriented in the same direction (i.e. parallel or 'ferromagnetically') cannot change the sign of their spontaneous magnetization when temperature rises from very low to TC. But ferrimagnets with oppositely oriented sublattices ('antiferromagnetically') sometimes exhibit the so called 'compensation point', between 0K and TN, where their spontaneous magnetization either changes sign or only just drops to zero. I have no practical experience with canted antiferromagnets, sometimes called 'weak ferromagnets'. They are even more curious: in some temperature interval (of course below critical temperature!) they spontaneously reorient their 'easy directions'. In result, the observed component of their magnetization (randomly selected) may change sign.
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