A magneto-caloric thermal diode assembly includes a magneto-caloric cylinder. A plurality of thermal stages is stacked along an axial direction between a cold side and a hot side. Each of the plurality of thermal stages includes a plurality of magnets and a non-magnetic ring. The plurality of magnets is distributed along a circumferential direction within the non-magnetic ring in each of the plurality of thermal stages. The plurality of magnets and the non-magnetic ring of each of the plurality of thermal stages collectively define a cylindrical slot. The magneto-caloric cylinder is positioned within the cylindrical slot. In each of the plurality of magnets in one of the plurality of thermal stages, a first, second, third and fourth magnet segments are positioned and oriented such that the first, second, third and fourth magnet segments collectively form a closed loop high-field zone across the cylindrical slot.