Experimental investigation of the quantum amplification effect for magnetostatic waves in ferrite-paramagnet structures

YIG magnonics

“…However, owing to the practical challenges of this technique (liquid helium temperatures and very high-frequency (cited 35.52 GHz) pumping of the ruby crystal) it has not been widely adopted. The amplification coefficient decreases from 25 to 12 dB with an increase in temperature from 1.6 to 4.2 K [103]. Moreover, no MSW amplification was observed in an epitaxial structure comprising a conventional YIG film grown on a gadolinium gallium garnet Gd 3 Ga 5 O 12 (GGG) substrate, which is explained by a strong paramagnetic absorption of MSWs in the GGG crystal at low temperatures.…”

“…A range of physical mechanisms for the amplification of travelling spin waves have been proposed and experimentally verified. These include quantum amplification of magnetostatic waves in ferrite-paramagnet structures [102,103], amplification of magnetostatic waves via interaction with drifting carriers (see e.g. [104][105][106][107][108][109] as well as a review by Kazakov and Filimonov [110]), and parametric amplification.…”

Microwave magnon damping in YIG films at millikelvin temperatures

“…However, in the case of YIG films grown on GGG, the story is more complex. GGG is a geometrically frustrated magnetic system [22] and it has long been known that at temperatures below 70 K, it exhibits paramagnetic behaviour that has been reported to increase damping in films grown on its surface [23][24][25]. The behaviour of GGG at mK temperatures is yet to be thoroughly characterised [26][27][28], but recent results at mK temperatures have suggested that magnon damping in YIG films grown on GGG is higher than expected if the properties of the YIG system alone are considered arXiv:1903.02527v3 [cond-mat.mes-hall] 25 Oct 2019 Dashed lines are linear fits, the details of these fits are summarised in table I.…”

Magnon Spintronics

“…Optical wavefront reversal involves second order, four-wave parametric interactions, pumped by counter-propagating optical beams with carrier frequencies close to that of the signal. In magnon systems, the process is achieved through first order, three-wave interactions [27,112,128].…”

“…Some, for example quantum amplification [111,112], and amplification through interaction with drifting carriers [113][114][115] are extremely interesting at the level of basic physics but, on account of their limited capability and the somewhat restricted applicability, have limited appeal in a device context. Others -most significantly the amplification of magnons through the spin-transfer torque effect [116][117][118][119][120] (see also "The Spin-Transfer Torque Effect") -are very attractive from an applications perspective but, at least in magnetic insulators [119,120], are still in the process of being properly understood [121].…”