Tsoi M, Jansen AG, Bass J, Chiang WC, Tsoi V, Wyder P
Grenoble High Magnetic Field Laboratory, Max-Planck-Institut fur Festkorperforschung and Centre National de la Recherche Scientifique, France.
Nature. 2000 Jul 6;406(6791):46-8. doi: 10.1038/35017512.
The magnetic state of a ferromagnet can affect the electrical transport properties of the material; for example, the relative orientation of the magnetic moments in magnetic multilayers underlies the phenomenon of giant magnetoresistance. The inverse effect--in which a large electrical current density can perturb the magnetic state of a multilayer--has been predicted and observed experimentally with point contacts and lithographically patterned samples. Some of these observations were taken as indirect evidence for current-induced excitation of spin waves, or 'magnons'. Here we probe directly the high-frequency behaviour and partial phase coherence of such current-induced excitations, by externally irradiating a point contact with microwaves. We determine the magnon spectrum and investigate how the magnon frequency and amplitude vary with the exciting current. Our observations support the feasibility of a spin-wave maser' or 'SWASER' (spin-wave amplification by stimulated emission of radiation).
铁磁体的磁态会影响材料的电输运性质；例如，磁性多层膜中磁矩的相对取向是巨磁电阻现象的基础。与之相反的效应——即大电流密度会扰乱多层膜的磁态——已通过点接触和光刻图案化样品进行了理论预测和实验观测。其中一些观测结果被视为电流诱导自旋波（即“磁振子”）激发的间接证据。在此，我们通过用微波对外照射点接触，直接探测此类电流诱导激发的高频行为和部分相位相干性。我们确定了磁振子谱，并研究了磁振子频率和振幅如何随激发电流变化。我们的观测结果支持了自旋波激射器或“SWASER”（受激辐射放大自旋波）的可行性。
