Antiferromagnetism conductivity

The second salt presents a structure where the anions occupy the tunnels formed by BEDT-TTF dimers. BEDT-TTF bears the unit positive charge. This salt behaves like a semiconductor with a very low room-temperature electric conductivity. The unpaired electrons on the organic cation-radicals are strongly antiferromagnetic coupled, giving rise to a diamagnetic behavior of the second salt, because the nitroprusside anion is also diamagnetic. 

The conduction band of an antiferromagnetic non-metal spin polarons... 

In this section we discuss the properties of an electron in the conduction band of an antiferromagnetic insulator. This may be a simple Mott insulator, but, since the experimental evidence is related to them, we first discuss materials like EuSe, where the europium ion has seven 4f-electrons and electrons can be introduced into the conduction band by doping with GdSe the ion Gd2 + has the same number of f-electrons but one more electron in an outer shell, so a Gd ion acts as a donor. 

Perhaps the most direct evidence of the high effective mass in such materials comes from the work of Shapira et al. (1972) on the conductivity of EuTe and the work of Shapira and Reed (1972) on EuS, an antiferromagnetic material, with sufficient non-stoichiometry to make it a degenerate n-type semiconductor. Figure 3.5 shows the temperature variation of the resistivity for various magnetic... 

Our model is thus of a metal, with a small number of carriers in the conduction band and 3d- or 4f-moments antiferromagnetically coupled to each other by direct exchange. The carriers may be either inserted by doping or by overlap from the lower Hubbard band (cf. Chapter 4, Section 3). The most striking prediction of the model, however, is that the degenerate electron gas should have a much enhanced Pauli magnetism. Suppose that EF is the Fermi... 

On the other hand, hopping conduction in antiferromagnetic insulators seems to be greatly affected by spin disorder, as shown by the work of Whall et al. (1987) on MnFe204, in which both dajdT and dS/dT show striking changes at the Neel temperatures (about 600 K). 

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