Theory 14/Magnetic Materials

Exchange Bias Is a Thickness Ratio

The claim

Exchange bias in a ferromagnet-antiferromagnet bilayer is set by the ratio of antiferromagnet thickness to domain wall width, vanishing when the layer is thin enough to rotate as a whole.

01The mechanism

Bias requires a frozen antiferromagnetic interface; if the layer is thinner than the wall width, the interface moments rotate with the ferromagnet and no bias survives.

02Predictions

P1Bias should vanish below a thickness ratio.
P2Thicker layers should saturate the bias.

03Refutation

Bias independent of the ratio would remove the wall mechanism.