The hysteresis loops of exchange-biased FeMn/Co bilayers have been measured by means of a superconducting quantum interference device magnetometer. The obtained right and left coercivities exhibit different temperature dependences. With temperature increasing, the left coercivity monotonously increases while the right one remains almost constant until a critical temperature Ti. Upon decreasing the thickness of the antiferromagnet (AF) layer, Ti decreases. The asymmetric behavior of the right and left coercivities indicates that the reversal mechanisms are different for increasing and decreasing field. By taking into account the temperature dependence of the spin alignment in the AF layer, the unusual asymmetric behavior is well explained.
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