Ferromagnetic and spin wave resonance at high pressure

Abstract

The pressure dependence of the magnetization (+0.105%/kbar), g value (+0.094%/kbar), and exchange stiffness D (+0.054%/kbar) have been measured by ferromagnetic and spin wave resonance from one bar to five kilobars at room temperature in 80-20 permalloy. Since the film is evaporated on a sapphire substrate, the film is not deformed hydrostatically but is strained −0.0293%/ kbar in thickness and −0.0106%/kbar in the transverse directions. When the pressure dependence of the magnetization is compared to hydrostatic determinations, the magnetization is found to be an anisotropic function of strain. Using the general Heisenberg model, the hydrostatic strain dependence of D (+0.067%/kbar) is derived from the experimental results. For the nearest neighbor Heisenberg model, the atomic distance dependence of the interatomic exchange [d(In J)/d(In a) = −5.2] is calculated from the results and compared to the pressure dependence of the Curie temperature, and the magnetic Gruneisen factor. The spin wave resonance results are also analyzed using the short range, single band itinerant electron model to determine the strain dependence of the band splitting parameter Δ (+0.048%/kbar).