Effect of Cu doping on the magnetic and magnetocaloric properties in the HoNiAl intermetallic compound

The magnetic properties and magnetocaloric effect of Cu doping on HoNiAl (HoNi1−xCuxAl) have been investigated. Two transitions occurred for samples with x = 0 and x = 0.1 induced by the combination and competition between antiferromagnetic (AFM) and ferromagnetic (FM) orderings. Simple AFM orderings were found in samples with x = 0.2 to x = 0.7 while FM orderings were found in samples with x = 0.8-1. The magnetocaloric effect (MCE) was investigated in selected samples with x = 0.3 and 0.8. Large magnetic entropy changes (ΔSM) as −29.2 J/kg K at 9 K and −19.7 J/kg K at 9 K with corresponding refrigerant capacity (RC) of 299 J/kg, 309 J/kg for a field change of 0-50 kOe were observed. The large ΔSM and RC without hysteresis loss indicated these materials attractive candidates for magnetic refrigeration in low temperature range.