Thermodynamics around the first-order ferromagnetic phase transition of Fe2P single crystals

The specific heat and thermodynamics of Fe2P single crystals around the first-order paramagnetic to ferromagnetic (FM) phase transition at TC?217K are empirically investigated. The magnitude and direction of the magnetic field relative to the crystal axes govern the derived H?T phase diagram. Strikingly different phase contours are obtained for fields applied parallel and perpendicular to the c axis of the crystal. In parallel fields, the FM state is stabilized, while in perpendicular fields the phase transition is split into two sections, with an intermediate FM phase where there is no spontaneous magnetization along the c axis. The zero-field transition displays a textbook example of a first-order transition with different phase stability limits on heating and cooling. The results have special significance since Fe2P is the parent material to a family of compounds with outstanding magnetocaloric properties