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中国物理学会期刊

铁氧体参量耦合振荡的理论分析

CSTR: 32037.14.aps.17.117

THEORY OF THE PARAMETRICALLY COUPLED OSCILLATIONS IN FERRITE

CSTR: 32037.14.aps.17.117
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  • 在本文中我们系统地讨论了铁氧体小样品在超高频电源的激发下产生参量振璗的耦合关系,指出激发机构应分为磁场驱动和磁化驱动二类。前者的特例为Denton新近发现的,使用空间均匀的纵向注入场;后者的特例为Suhl最早所研究的,使用空间均匀的横向注入场所激发的一致进动的磁化向量为驱动力。从静磁势函数的耦合微分方程我们得到这二种特殊注入方式激发的静磁势函数的完全解(一次近似),表达为Walker函数的线性组合,在边界连续的要求下,这些势函数中的Walker模只在它们的指标之间适合一定的条件时才相互关联。当直流磁场调谐于一对Walker模时,耦合的静磁势简化为静磁操作的势函数。我们具体分析了静磁操作参量振璗从注入场吸取的功率,根据后者必须不为零才可能产生参量振璗,我们推导出空间均匀场激发一对静磁模的选择定则,恰与从边界连续推出的关联条件完全相同,并且进一步得到空间不均匀场激发一对静磁模的选择定则。我们指出,参量振璗的振幅的决定必须引用能量守恒和量子数相等的方程。最后我们采用Suhl的方法推算出空间均匀的纵向注入场的激发临阈强度,并且讨论了这一方法的近似性质。

     

    In this article the parametrically coupling of oscillations in a small ellipsoid of ferrite under the excitation of an uhf pumping of any spatial distribution is discussed. It is pointed out that the coupled oscillations may be induced through the two types of driving, field driving and magnetization driving. A special case of the former was recently discovered by Denton, who used a longitudinal pumping field uniform in space. A special example of the latter is found in Suhl's theoretical analysis and a number of experimental works after him. The pumping field transverse in direction and spatially uniform does not induce the coupled oscillations directly, but the rf magnetization of the Kittel precession excited by the pumping becomes the driving force of the oscillations. For each type of a uniform pumping we obtain from a set of differential equations the magnetostatic potential functions (the first order approximation) as linear combinations of Walker's functions. These solutions are different from those given by MOHOCOB. Making. use of the boundary conditions at the ferrire surface we find that for the Walker modes involved in the oscillations to be coupled, thtir indices must satisfy certain condi'ions. For the case of magnetostatic operations the dc magnetic field is tuned to a pair of the Walker modes, the potential functions may be reduced greatly. By studying the power drawn by the coupled oscillations from the pumping, we obtain the selection rules of a pair of magnetostatic modes excited by a pumping field of any given spatial distribution. We point out that for the determination of the amplitudes of the oscillations the equations derived from the conservation of energy and from the equality of the number of quanta emitted must be used. Finally, the threshold intensity of Denton's pumping field is derived using Suhl's method. We indicate that this method is based on a perturbation calculation.

     

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