  We investigate thermal transport in a two segment classical Heisenberg spin
chain with nearest neighbor interaction and in presence of external magnetic
field using computer simulation. The system is thermally driven by heat baths
attached at the two ends and transport properties are studied using an energy
conserving dynamics. We demonstrate that by properly tuning the parameters
thermal rectification can be achieved - the system behaves as a good conductor
of heat along one direction but becomes a bad conductor when the thermal
gradient is reversed and crucially depends on nonlinearity and spatial
asymmetry. Moreover, suitable tuning of the system parameters gives rise to the
counterintuitive and technologically important feature known as the negative
differential thermal resistance (NDTR). We find that the crucial factor
responsible for the emergence of NDTR is a suitable mechanism to impede the
current in the bulk of the system.
