smart materials structure systems, Florence, İtalya, 10 - 14 Haziran 2012, ss.75
Inverse magnetocaloric effect in Mn3GaC at the thermally hysteretic magnetostructural transition
Ö. Çakır* and M. Acet, Physics Dept., Yıldız Technical University, Istanbul, Turkey; Experimental Physics, Duisburg-Essen University, Duisburg, Germany
The ferromagnetic to antiferromagnetic transition on decreasing temperature in the antiperovskite Mn3GaC is accompanied by a structural distortion which leads to thermal hysteresis. This magnetostructural transition occurs in the temperature range 150 ≤ T ≤ 170 K and has a thermal hysteresis-width of about 4 K as observed from magnetization measurements made in a small, 50 mT external magnetic field. The transition shifts to lower temperature under higher applied fields, namely by -4.4 TK-1. This shift is accompanied by a field-induced reverse transformation from the antiferromagnetic to the ferromagnetic state, giving rise to the inverse magnetocaloric effect. We study the inverse magnetocaloric effect, both by determining the entropy change from magnetization isotherms and by direct temperature-change measurement around the transition. We further study the properties of the thermal hysteresis by magnetization measurements and relate them to the observed temperature-change properties.