Magnetostriction of Paramagnetic Transition Metals. II. Group-VIII Metals Ru, Rh, Pd, Ir, Pt, and Their Alloys

The longitudinal magnetostriction of group-VIII transition metals and alloys was measured with a capacitance dilatometer at 4.2 °K in fields up to 100 kOe. The resultant values of the logarithmic volume dependence of the magnetic susceptibility, $\frac{\partial \ln \chi }{\partial \ln V}$, are Ru, -4.8; Rh, 9.6; Pd, -3.4; Ir, 22; Pt, -15; ${\mathrm{Rh}}_{50}$ ${\mathrm{Ir}}_{50}$, 15; ${\mathrm{Rh}}_{50}$ ${\mathrm{Pd}}_{50}$, 8; ${\mathrm{Ir}}_{40}$ ${\mathrm{Pd}}_{40}$, 14; ${\mathrm{Pd}}_{67}$ ${\mathrm{Pt}}_{33}$, -4; and ${\mathrm{Pd}}_{33}$ ${\mathrm{Pt}}_{67}$, -24. Pd, Pt, and their alloys have a negative magnetostriction, which indicates a negative volume dependence of the Coulomb interaction responsible for the exchange enhancement of their spin susceptibility. Rh, Ir, and their alloys with each other and with Pd have a positive magnetostriction, and the resultant large volume dependence of the susceptibility, particularly that of Ir, is difficult to understand. Float-zoned samples of Rh and Ir exhibit oscillatory de Haas-van Alphen magnetostriction at 4.2 °K.