Study of the first paramagnetic to ferromagnetic transition in as prepared samples of Mn-Fe-P-Si magnetocaloric compounds prepared by different synthesis routes

摘要

Magnetocaloric materials with composition of Mn_(1.3)Fe_(0.65)P_(0.5)Si_(0.5) have been prepared by ball milling and solid-state reaction methods and consolidated using powder annealing, and conventional and spark plasma sintering. Magnetic and calorimetric measurements show remarkable differences upon first cooling, and slight differences on second and further coolings between the samples prepared by different synthesis routes. Further measurements using Hall probe imaging in high magnetic field have been also carried out. As-prepared samples have been cooled down just above the critical temperature, and the first phase transition has been induced by application of a magnetic field. Bulk samples show staircase isothermal magnetization curves whereas powders show smoother transition curves.