First order phase transition in MnAs nanodisks

The first order phase transition between ferromagnetic amp; 945; MnAs and paramagnetic amp; 946; MnAs in nanoscale disks etched out of an epitaxial MnAs film on GaAs 001 is studied by means of X ray diffraction and magnetic force microscopy. The temperature hysteresis loop is observed to be expanded with decreasing disk size. The hysteresis is absent in the original continuous epitaxial film from which the disks are fabricated. The hysteresis is explained as a competition between the energy gain due to the phase transition and the energy loss due to the elastic strai