Exchange coupling between two magnetic films separated by an antiferromagnetic spacer

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Abstract
An expression for the interaction strength between two magnetic films separated by an insulating antiferromagnet spacer has been derived as a function of temperature and thickness. We consider the mechanism wherein the magnetic interaction between the ferromagnetic layers is mediated by the intervening antiferromagneticinsulator via the Suhl–Nakamura (SN) interaction. The interaction energy per unit area, σ SN , is derived as σ SN = 1 8 (J C 2 /J AF )(δ/a) exp (−t/δ). Here, J AF is the magnetic coupling constant between nearest-neighbor antiferromagnetic spins in the spacer, J C is the effective coupling constant (which is greatly reduced from the Heisenberg exchange constant), between the spins in the ferromagneticfilm and the nearest-neighbor spins in the antiferromagnetic spacer, t is the separation of the two ferromagnetic plates, and δ is the width of an antiferromagneticdomain wall. This mechanism is the antiferromagnetic analog of the Ruderman–Kittel oscillatory coupling between two magnetic films separated by a normal metal.