We report on anisotropy measurements of FePt thin films prepared at different temperatures and find that the anisotropy increases with increasing chemical ordering. Within measurement accuracy, we conclude that the second-order anisotropy constant K_2 is negligibly small compared to the first-order anisotropy constant K_1. We assert that the presence of a small hard-axis hysteresis causes spatial fluctuations of the field direction within the sample, which changes the shape of the hard-axis loop, such that it is misinterpreted as a K_2 in the Sucksmith-Thompson formalism.
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