Winton Meeting on Caloric Materials, London, İngiltere, 10 - 11 Şubat 2016, ss.7
Hysteresis in magnetocalorics
M. Acet1, F. Scheibel1, A. Tekgül2, M. Riebisch1, Ö. Çakır3, R. Meckenstock1, D. Spoddig1, T. Gottschall4, K. P. Skokov4, K. Ollefs1,H. Wende1, O. Gutfleisch4, M. Farle1
1Experimentalphysik, Universität Duisburg-Essen, 47048 Duisburg, Germany
2Physics Department, Akdeniz University, 07000 Antalya, Turkey
3Physics Department, Yıldız Technical University, 34220 Istanbul, Turkey
4Materialwissenschaft, TU Darmstadt, 64287 Darmstadt, Germany,
Hysteresis in any generalized displacement variable as a function of the conjugated field is a source of dissipation. In the particular case of magnetocalorics, adiabatic temperature changes relying on the presence of first order magnetostructural transitions are subjected to the adversities of the related transitional hysteresis. To be able to design suitable magnetocaloric materials, it is necessary either to overcome hysteresis totally or to ‘live with’ hystereses that are sufficiently narrow. We present here, first, the various steps occurring in the adiabatic temperature-change process when a magnetic field is applied and removed cyclically at first order magnetostructural transitions. Then we examine the cause of hysteresis, particularly in relation to the nature of magnetic coupling around the magnetostructural transition. The experimental thermodynamic and spectroscopic investigations are undertaken in martensitic Heuslers, antiperovskite manganites, and manganese-based pnictides.