Abstract

Nonlinear Interaction of Magnetoelastic Waves in Porous Ferrites

S.N.Karpachev, A.I.Yafasov (Department of Acoustics, Faculty of Physics, Moscow State University, Moscow, Russia)

e-mail: snk@snk.phys.msu.su

It is known that at conditions of magnetoacoustic resonance (MAR) the effective magnetoelastic (ME) nonlinearity increases by several orders. This results in effective generation of spin-response signal, produced by encountering ME-waves nonlinear interaction. All previous experiments were conducted on single-crystal ferrites. Here we report some results of our experiments on polycrystalline ferrites. We used samples of Ni-Zn ferrite with different porosity. ME-waves were generated by LiNbO3 transducers, fed with 30 MHz RF-pulses. The resulting 60-MHz spin response signal was received using a coil wrapped around the specimens and measured as function of external magnetic field H. The experiments show that the width of this signal line (in respect to H) linearly increases as the function of porosity. At the same time, the resonance field value (corresponding to a maximum of the signal) linearly decreases. Some parallels can be made between our experiments and those concerning the influence of porosity on FMR line width. The main difference (aside from methods of excitation) is that MAR can be excited in specimen locally. This can be done by applying a time delay to one of ME-waves in our experiment. Thus, application of acoustic waves can be helpful in investigation of local porosity.

Section : 2