7th International Conference on Magnetic Refrigeration at Room Temperature (Thermag VII), Turin, İtalya, 11 - 14 Eylül 2016, ss.352
Hysteresis at first order transitions in Mn3GaC and Mn3GaC0.85N0.15 studied by adiabatic temperature change and polarized neutrons
Ö. Çakır(a)*, F. Scheibel(b), F. Cugini(c), M. Solzi(c), M. Acet(b)
(a) Physics Dept., Yıldız Technical University, 34220 Istanbul, Turkey (b) Physics Dept., Duisurg-Essen University, 47048 Duisburg, Germany
(c)Dept. of Physics and Earth Sciences, University of Parma, 43124 Parma, Italy
*Corresponding author. E-mail: email@example.com
Partially substituting carbon by nitrogen in the antiperovskite compound Mn3GaC increases the first order antiferromagnetic/ferromagnetic magnetostructural transition temperature from about 160 K to close to room-temperature and at the same time causes the high- temperature long-range ferromagnetism to weaken. We present here results on adiabatic temperature-change measurements on Mn3GaC and Mn3GaC0.85N0.15 obtained under slow and fast (pulsed) magnetic field changes and discuss the kinetics and time-windows involved in the transition. We further show by neutron depolarization and neutron polarization analysis experiments on Mn3GaC and Mn3GaC0.85N0.15 that the weakening of the ferromagnetism is related to the diminishing of ferromagnetic domain formation. We combine the results to extract information on the transitional hysteresis and the kinetics of the transition. The relationship between ferromagnetic domain formation and transitional hysteresis is brought forward for these two important magnetocaloric materials.