Magnetic behavior of half-Heusler alloy CuxNi1-xMnSb

We have investigated the effects on the magnetic properties of NiMnSb alloys with the substitution of Cu for Ni. The half-Heusler type alloys, CuNi1-xMnSb compounds, are fabricated by the arc-melting method and are subsequently annealed at a temperature of 1050 K for 24 It. It was found that at a temperature of 4 K and field of 10 k Oe for CuxNi1-xMnSb samples, the formula moment remains almost unchanged for x<0.7. With x increasing above 0.7, the formula moment starts to decrease. The Curie temperature and susceptibility for different Cu compositions were measured on SQUID. The paramagnetic Curie temperature is obtained by extrapolation. It shows that the Curie temperature dependence of Cu composition is similar to that of paramagnetic Curie temperature versus Cu composition, which decreases with increasing Cu composition. The relation between Curie temperature and Cu composition can be fitted with the formula, T-C = A-Bx(2), which reflects the weakening in exchange energy with substitution of Cu for Ni in NiMnSb alloys. The temperature dependence of susceptibility fitted at high temperature for different Cu compositions shows that with the substitution of Ni by Cu the Curie constant remains almost unchanged which indicates that the total angular momentum and effective moment remain almost unchanged. The laws of temperature dependence of susceptibility are consistent with that of magnetism versus temperature, which originates from the effects of Curie temperature for different Cu compositions. When Cu compositions increases from x = 0 to 1, the magnetic properties of the alloys change from ferromagnetism to ferrimagnetism. When x=1 antimagnetism for the sample is exhibited. (C) 2004 Elsevier B.V. All rights reserved.