DM/DT MEASUREMENTS IN FERROMAGNETIC PD(FE)

An ac temperature technique is employed in direct measurements of ∂M/∂T for a 1%(at.) Fe in Pd sample whose Curie temperature is 40-50°K. Temperatures between 1.5° and 4.2°K and fields up to 30 kG are employed. The temperature and magnetic field dependences of ∂M/∂T are analyzed to obtain the spin-wave exchange stiffness coefficient D. The temperature dependence of ∂M/∂T extrapolated to H = 0 gives D≃550±34(°K - Å2) in good agreement with independent measurements on alloys of similar iron concentration. A point by point analysis of ∂M/∂T in H≳5 kG, however, yields a strong (T, H) dependence for D and suggests that a simple spin-wave description is not applicable. If we separate a spin-wave component with D=550(°K - Å2) and g = 2 from the measurement, the remaining component of ∂M/∂T is not neglibigle and has a strong (T, H) dependence even at 30 kG. © 1969 The American Institute of Physics.