Abstract:
The magnetic, magnetocaloric, and magnetoresistive properties of the polycrystalline compound HoNiAl have been studied. The temperature variations of magnetization and heat capacity show that the compound undergoes two magnetic transitions, one at 14 K and the other at 5 K. The former is due to the paramagnetic-ferromagnetic transition, while the latter is attributed to the onset of an antiferromagnetic ordering, as the temperature is lowered. The M-H isotherm obtained at 2 K shows a metamagnetic transition with a critical filed of about 13 kOe. The maximum values of isothermal magnetic entropy change and adiabatic temperature change, for a field change of 50 kOe, are estimated to be 23.6 J/kg K and 8.7 K, respectively. The relative cooling power is found to be about 500 J/kg for a field change of 50 kOe. A large magnetoresistance of about 16%, near the ordering temperature of 14 K, is observed for a field of 50 kOe. The magnetic, magnetocaloric, and magnetoresistance data seem to suggest the presence of magnetic polarons in this compound. (C) 2007
