Exercises 14.2: Antiferromagnetism

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A) . . B)

14.2.1 The figures are for the system with the Ising spins orienting perpendicular to the plane of the array and with a 1/r^3 dipolar interaction. Only the magnitude of the dipolar interaction has been changed going from one to the other. The exchange interaction remains the same.

A) For these patterns, is the exchange interaction ferromagnetic or antiferromagnetic in sign?

B) For which case is the dipolar interaction stronger?

C) Has the dipolar interaction of any spin with all the others been chosen to be ferromagnetic or antiferromagnetic in sign?