Dear RG members,
I read in literature that 2theta peaks of doped oxide may shift to lower or higher angles as the doping concentration increase due to the ionic differences between cations of the dopant and host lattice. Transition metals have high and low spin states, in each state TM has two different ionic radius. So, Is it correct to predict the spin state from peak shifting based on ionic radius difference where chemical pressure may play a crucial rule in this case?
thanks in advance
When the spin state of the material changes, there will be a volume collapse that may alter the crystal structure. Have a look at the following article. But XRD won't provide any informtion about high spin or low spin, for that you need to carry out X-ray emission spectroscopy
http://www.pnas.org/content/111/14/5106
Dear M M Obeid,
From X-ray diffraction pattern you can not predict any type of magnetic structure. You may say one can not predict high or low spin state of the transition metal as X-rays do not have any magnetic moment. You can predict the high or low spin state from neutron diffraction rather than X-ray or after magnetization measurements.
Dear Dr. Sorb Yesudhas , the volume of doped sample decrease as the doping concentration increase. Is the chemical pressure due to doping cuase the transition change of the dopant spin state that lead to volume collaps ?
Mohammed M. Obeid @ Yes, you are right. Doping generates chemical pressure just like hydrostatic pressure. Usually when you dope, either compression or expansion of the lattice take place depending on the size of the dopants. The volume decrease doesn't mean that change of spin state (nothing but lattice compression). When the spin state changes, there should be some anomaly in the lattice. It can be lattice parameter anomaly (causing volume change) or huge volume drop (collapse). If the spin state flips to 180 degree, it can produce volume collapse. Tilting of the spin produces lattice anomaly (antiferromagnetic).
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