Effect of Fe substitution on the magnetic characteristics of some RNi5alloys (R = Pr and Nd)

The magnetic properties of PrNi
4
Fe and NdNi
4
Fe have been studied at temperatures ranging from 4 to 300 K and at field strengths up to 21 kOe. Replacement of 20% of the Ni by Fe in PrNi
5
and NdNi
5
expands the lattice and produces a significant alteration in magnetic behavior. PrNi
5
is a Van Vleck paramagnet and NdNi
5
is a weak ferromagnet, Curie temperature = 13 K. In contrast, PrNi
4
Fe and NdNi
4
Fe are found to develop ferromagnetic order at low temperatures with Curie temperatures of 230 and 285 K, respectively. Saturation magnetizations at 4.2 K are found to be 7.0 and 7.3 μ
B
per formula unit for PrNi
4
Fe and NdNi
4
Fe, respectively. The magnetic behavior of these systems indicates that Fe induces a moment on the neighboring Ni atoms of about 0.65 μ
B
/Ni atom. The magnetization-temperature plots obtained for both systems below the Curie point, at 4 kOe applied field, show maxima. The maxima disappear in an applied field of 21 kOe, and hence they are attributed to the increased magnetic hardness at low temperatures.