DCMPMS Seminars

Investigation of the magnetic, exchange bias and magnetocaloric properties in certain Mn-Ni based full Heusler systems

by Ms. Jyoti Sharma (Research Associate, Department of Physics, I.I.T., Bombay, Mumbai)

Thursday, May 4, 2017 from to (Asia/Kolkata)
at AG80
Description
Structural, microstructural, magnetic, exchange bias and magnetocaloric properties of various         Mn-Ni-Sn based full Heusler systems in their bulk and melt spun ribbon forms have been investigated. In recent years, Heusler alloys (intermetallic compounds) have attracted tremendous attention owing to their multifunctional properties such as shape memory effect, large magnetocaloric effect (MCE), exchange bias (EB) and giant magnetoresistance etc., which find various potential applications such as in magnetic refrigeration, shape memory and spintronic devices. Most of the properties are associated with their first order structural (i.e. martensitic) transition from high temperature austenite to low temperature martensite phase. 

Magnetic nature of Mn-Ni-Sn Heusler systems has been studied by DC magnetization and AC susceptibility measurements. Frequency dependence of spin freezing temperature on the scaling law and the study of memory and aging effect confirm the presence of spin glass-like ground state in the present alloys. This is attributed to the observation of large EB effect in these alloys. Some of the compositions have been found to show MCE around room temperature. During the experimental study, it is also found that other transition metal elements such as Co substitution in these alloys show the significant change in AFM/FM exchange interactions, which showed the improvement in various physical and magnetic properties. At the same time, changing the grain size by melt spinning technique was found to enhance the EB and change in other physical properties significantly as compared to their respective bulk counterparts. Therefore the present results indicate that the composition, temperature, and magnetic field controllability, and low cost render these Heusler alloys truly multifunctional from fundamental research as well as application point of view.