Answer to Question #178889 in General Chemistry for sughnen

Question #178889

Consider the cubic perovskite LaFeO3, in which the iron center is high-spin.

a. Do you expect a Jahn-Teller distortion? Why or why not?

b. Do you expect the interactions between iron centers to be ferromagnetic or antiferromagnetic? Explain why, and show the orbital pathways involved in the magnetic interactions.

c. Sketch qualitatively what the magnetic susceptibility (χ) of this compound would look like as a function of temperature.

Expert's answer

The surfaces of transition-metal oxides with the perovskite LaFeO3, Fe3+ is present in a high-spin state with octahedral.

Fe3+ is high-spin in most cases, e.g. in Fe_3O_4, with a d^5 electron configuration and occupies tetrahedral or octahedral sites. The Jahn-Teller effect will lead to a distortion from octahedral to some lower symmetry where the t2g orbitals split up.

The popular understanding of a magnetic material is ferromagnetism, such as in iron, Fe. Therefore, two electrons paired in the same orbit must have one up and one down spin - the net spin and therefore the magnetism being zero. If, at the end, one unpaired electron remains, the atom has a net spin and is magnetic.

Magnetic susceptibility of diamagnetic substance is negative but with small magnitude. Also magnetic susceptibility of diamagnetic substance does not depend on temperature i.e K=constant with temperature.

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