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Ferromagnetic Resonance in Yttrium Iron Garnet at Low Frequencies

机译：低频下钇铁石榴石的铁磁共振

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Single crystals of yttrium iron garnet (YIG) exhibit the narrowest resonant line of all known ferromagnetic materials, being as low as 2.3 oe for the full width at half height for polished spheres at 9300 mc. Ferromagnetic resonance on polished YIG disks was observed at frequencies as low as 44 mc, for an applied dc field of 1000 oe. Conversely, resonance was observed for fields as low as 300 oe, for a frequency of 2000 mc. Nonlinear effects in ferromagnetic materials can be evidenced by the excitation of unstable spin wave modes, such as were discovered at x band by Bloembergen and his colleagues. In their case the dc fields required for this subsidiary resonance were approximately one half that required for resonance of uniform precession. When measurements are made on a sphere at a frequency low enough so that Hres≪8πMs/3, Suhl''s theory shows that the dc field required for the minimum threshold of the subsidiary resonance is identical with that required for resonance of the uniform precession. In this case the critical rf fields required are particularly low being given in terms of the line width to an order of magnitude as hcrit=ΔH2/4πMs. Measurements have been made of hcrit, for the subsidiary resonance as a function of frequency for polished single crystal spheres of YIG. Based on a 4πMs of 1725, the frequency below which coincidence of the uniform precession and subsidiary resonances occur, is 3220 mc. Below 1610 mc the dc fields for resonance are insufficient to saturate the sphere and domains are formed. Values are given for hcrit, spin-wave angle θ, and spin-wave number k for frequencies of 1610 to 3220 mc. At 2200 mc a min in hcrit occurs. At this frequency hcrit=2.0 millioersteds, the power incident on the cavity is 20 m-nicrowatts and the power absorbed by the sample is of the order of a microwatt. The experimental results are discussed in terms of Suhl''s theory.
机译：钇铁石榴石（YIG）的单晶表现出所有已知铁磁材料中最窄的谐振线，对于9300 mc的抛光球，其半高全宽低至2.3 oe。对于1000 oe的直流磁场，在低至44 mc的频率下，在抛光的YIG圆盘上观察到铁磁共振。相反，在频率为2000 mc的低至300 oe的磁场中观察到共振。铁磁材料中的非线性效应可以通过激发不稳定的自旋波模式来证明，例如Bloembergen及其同事在x波段发现的。在这种情况下，该次要共振所需的直流磁场约为均匀进动共振所需的直流磁场的一半。当以足够低的频率在球体上进行测量以使Hres≪8πMs / 3时，苏尔的理论表明，子共振最小阈值所需的直流磁场与均匀进动共振所需的直流磁场相同。在这种情况下，所需的临界rf场特别低，就线宽而言，给出的数量级为hcrit =ΔH2/4πMs。已经测量了hcrit，以测量YIG抛光的单晶球的次谐振与频率的关系。基于1725的4πMs，低于该频率的频率为3220 mc，均匀的进动和辅助共振同时发生。低于1610 mc，共振的直流磁场不足以使球体饱和，并形成畴。对于1610至3220 mc的频率，给出了hcrit，自旋波角θ和自旋波数k的值。在2200 mc时，hcrit出现最小值。在此频率hcrit = 2.0毫托时，入射到腔体上的功率为20 m尼瓦，样品吸收的功率为微瓦量级。根据苏尔的理论讨论了实验结果。

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    《Journal of Applied Physics》 |1958年第3期|共2页
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  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);
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