Magnetic susceptibility studies of the (Cr₈₄Re₁₆)_100−xV_x alloy system

The temperature dependence of magnetic susceptibility, χ(T), of the (Cr₈₄Re₁₆)_100−xV_x alloy system is reported in this contribution. Anomalies are observed at the Néel temperature (T_N), associated with the onset of the antiferromagnetic (AF) spin-density-wave (SDW) state, with these anomalies becoming more pronounced as x increases. The T_N values determined from χ(T) measurements are in close agreement with that obtained from the measurement of temperature dependence of electrical resistivity, ρ(T). Prominent broad deep minima are observed in χ(T) upon cooling below 100 K which are followed by low temperature peaks in x = 10.4, 10.9 and 12.4 samples. A second anomaly, not associated with T_N, is observed at a temperature T_O < T_N for alloys with x = 0, 1.3, 2.4, 4.4, 5.7 and 6.9. This anomaly at T_O has a trend that resembles that at T_N suggesting that it too is associated with an AF phase. T_O observed in the x = 0 alloy has value of 309 ± 2 K which is very close to 308 K, the transition temperature of AF Cr₂O₃. However, as the value of T_O obtained from χ(T) decreases with an increase in x, it is an indication that the oxide is most likely a V-doped oxide of Cr, (Cr_100−δV_δ)₂O₃. The plots of x dependence of T_N obtained from ρ(T) and χ(T) measurements were fitted with a power law of the form T_N = a(x_c – x)^b yielding a = 135 ± 24 K, b = 0.59 ± 0.01, a critical exponent, and x_c = 10.47 ± 0.03, the critical concentration at which antiferromagnetism (AFM) disappears. It is therefore evident that the low temperature peaks for samples with x = 10.9 and x = 12.4 are associated with the (Cr_100−δV_δ)₂O₃ oxide whereas that of the x = 10.4 sample corresponds to T_N of the sample. Curie-Weiss (CW) behaviour was tested by plotting χ⁻¹ as a function of T and fitting the CW equation to the experimental data above T_N. A positive gradient of the fit confirms CW behaviour which was observed in the x = 5.7, 10.4, 10.9 and 12.4 alloys suggesting the existence of local moments at T > T_N.