  Recently there is a lot of attention given to manipulation of heat by
constructing thermal devices such as thermal diodes, transistors and logic
gates. Many of the models proposed have an asymmetry which leads to the desired
effect. Presence of non-linear interactions among the particles is also
essential. But, such models lack analytical understanding. Here we propose a
simple, analytically solvable model of a thermal diode. Our model consists of
classical spins in contact with multiple heat baths and constant external
magnetic fields. Interestingly the magnetic field is the only parameter
required to get the effect of heat rectification.
