Some models for exchange bias at the interface of a ferromagnet and antiferromagnet involve the formation of partial domain walls in the antiferromagnet layer. Numerical calculations of mean-field temperature dependence are used to examine thermally induced instabilities in the partial domain wall at ideal compensated and uncompensated antiferromagnet interfaces. At compensated interfaces, depinning of the partial wall results in a total loss of bias. At uncompensated interfaces, thermal effects at the interface cause the wall to move into the antiferromagnet. The critical fields for this partial depinning are different for the forward and reverse magnetization directions. This mechanism on uncompensated interfaces allows for simultaneous loop shift and coercivity, which is not found in the compensated case. (C) 2001 American Institute of Physics.