Large exchange bias from coupled antiferromagnetic order and glassy magnetic freezing in $C{o}_{0.36}Nb{S}_2$

Magnetization measurements on single-crystalline $C{o}_{0.36}Nb{S}_2$ reveal antiferromagnetic order near $T_N\simeq 26K$ and a lower-temperature history-dependent magnetic response consistent with glassy freezing of a subset of magnetic moments. After field cooling, $M(H)$ loops exhibit a sizable exchange-bias shift, reaching $\mathrm{\mid }{H}_{EB}\mathrm{\mid }\simeq 4.4kOe$ at $1.8K$ for a $70kOe$ field-cooling sweep protocol. The training effect, field-sweep and cooling-field protocol dependence, and disappearance of the bias near a blocking temperature $T_B\simeq 12K$, well below $T_N$, support an interpretation in which frozen uncompensated moments are exchange-coupled to an antiferromagnetic matrix. These results suggest that antiferromagnetic-glassy-moment coupling may provide a broader route to exchange bias in off-stoichiometric magnetic $Nb{S}_2$ intercalates.