Magnetocaloric Effect with Very Small Magnetic Hysteresis Losses of CoMn1-xTixGe Alloys

The effects of Ti substitution for Mn and heat treatment on structural, magnetic and magnetocaloric properties of CoMnGe alloy have been investigated by electron microscopy, X-ray diffraction, calorimetric and magnetic measurements. According to X-ray diffraction measurements, the CoMn1-xTixGe alloys are in a single phase, hexagonal structure at room temperature. It is found that the as-cast CoMn0:95Ti0:05Ge alloy shows a magnetostructural phase transition close to room temperature. The transition shows a large magnetic entropy change and a small hysteresis in the isothermal magnetic field dependent magnetization measurements. Upon annealing, the transition temperature decreases slightly. The decrease in temperature is accompanied by a significant increase in the magnetic entropy change, i.e., magnetic entropy change at 1T field change was increased from -3.3 J/Kg.K to -6.3 J/Kg.K. Moreover, after annealing, hysteresis losses reduced significantly for delH=7 T. Accordingly, we report that the heat treatment has a significant effect on magnetocaloric properties of the CoMn0:95Ti0:05Ge alloy.