The Double Exchange Mechanism

In the case of the mixed-valence manganites with the perovskite stracture, Zener s double-exchange (DE) mechanism has been used to explain the CMR effect (Zener, 1951c). In this model, a strong Hund s coupling is presumed to exist between the itinerant 

In LnMnOa + s, manganese disproportionates via 2Mn Mn + Mn . Doping of the Ln and Mn sites with Sr and Ru has been found to suppress this reaction and, 

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The fact that LSMO is ferromagnetic in the charge-ordered, insulating state is remarkable, since it indicates that the ferromagnetic interaction at low temperatures cannot arise from the double exchange mechanism. We note here that other... 

A mechanism to account for the parallel spin alignment between the Fe in the octahedral site and the octa-hedrally coordinated Fe was proposed by Zener and is called the double exchange mechanism. The idea is that an electron from the Fe ion (3d ) is transferred to the oxygen in the face-centered position of the subcell shown in Figme 33.12. At the same time there is transfer of an... 

Zener, C (1951) Interaction between the d-shells in the transition metals, Phys. Rev. 81,440 and Interaction between the d-shells in the transition metals 2 Ferromagnetic compounds of manganese with perovskite structure, Phys. Rev. 82, 403. These two papers have been cited collectively almost 4000 times and describe the double exchange mechanism. Clarence Zener spent a short time (1940-1942) as an instructor at Washington State University when it was still known as Washington State College. 

At higher temperatures, the ordering forces involved in the double exchange mechanism are disrupted by thermal agitation. Eventually this overcomes the... 

The double exchange mechanism has been successfully used to explain the ferromagnetism observed in (In,Mn)As [65, 72, 73]. In a DMS material, if... 

Sato and Katayama-Yoshida [68] performed first principles ab initio calculations of the electronic structures of TM-doped ZnO and proposed the double exchange mechanism for the carrier-induced ferromagnetism. The first principles calculations predict that transition metals V, Ct Fe, Co, and Ni-doped ZnO [87] showed ferromagnetism with concentration from 5 to 25%, whereas the Mn-doped ZnO shows spin-glass state at ground state because of the exact half-filled d state of Mn ions [68]. For comparison, Cr +, Fe +, Co +, and Ni have d, d, d, d, and... 

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