Microwave Oscillators and Detectors Based …
37
Fig. 24 a Simulated STFMR spectra accounting for the VCMA effect for an in-plane external
field, H = −1000 Oe, I dc = 0.2 mA and P rf = −42 dBm. The obtained sensitivity is of the order
of 10 5 mV/mW. The inset shows the clamshell trajectory at the two extreme points in the STFMR
spectra. b shows the excited frequency of the MTJ as a function of the driving RF signal clearly
showing parametric synchronization in the shaded region with a locking bandwidth, f bw . Reprinted
from Sisodia et al. [162], with permission from AIP Publishing
for a perpendicular MTJ with VCMA at an external in-plane field of H = −1000 Oe.
The applied dc bias of I dc = 0.2 mA is above the threshold dc bias (I th = 0.13 mA)
for auto-oscillations which is a necessary requirement for this method. The injected
power is −42 dBm. Figure 24b shows the parametric synchronization, where the
excited frequency is exactly half of the driving frequency in a certain bandwidth
(f bw ). Using parametric synchronization, along with an increase in sensitivity, the
detection frequency is also enhanced since the RF signal being detected is close to
2f 0 . Numerical simulations predict that the sensitivity values in this case will also
be of the order of 10
5 mV/mW with comparably much higher detection frequencies
(4–6 GHz).
The values of sensitivity and detection frequency obtained by the above discussed
methods are summarized in Table 1. These results suggests that VCMA together with
parametric synchronization offer best combination of high RF sensitivity as well as
high detection frequency.
10 Spin Hall Nano-oscillators
In 1999, Hirsch revisited [164] a different phenomenon, the so-called spin Hall effect
(SHE), first described by D’yakonov and Perel’ in 1971 [165, 166]. The SHE can
produce a pure spin current in a direction perpendicular to a charge current [167,
168], which can, in turn, exert substantial STT on an adjacent magnetic layer. It
is thus possible to use the SHE in a nonmagnetic metal to achieve, in principle,
all the STT-related functions-such as magnetic switching [169, 170] and driven
magnetization precession [171, 172] that previously required a separate magnetic
37
Fig. 24 a Simulated STFMR spectra accounting for the VCMA effect for an in-plane external
field, H = −1000 Oe, I dc = 0.2 mA and P rf = −42 dBm. The obtained sensitivity is of the order
of 10 5 mV/mW. The inset shows the clamshell trajectory at the two extreme points in the STFMR
spectra. b shows the excited frequency of the MTJ as a function of the driving RF signal clearly
showing parametric synchronization in the shaded region with a locking bandwidth, f bw . Reprinted
from Sisodia et al. [162], with permission from AIP Publishing
for a perpendicular MTJ with VCMA at an external in-plane field of H = −1000 Oe.
The applied dc bias of I dc = 0.2 mA is above the threshold dc bias (I th = 0.13 mA)
for auto-oscillations which is a necessary requirement for this method. The injected
power is −42 dBm. Figure 24b shows the parametric synchronization, where the
excited frequency is exactly half of the driving frequency in a certain bandwidth
(f bw ). Using parametric synchronization, along with an increase in sensitivity, the
detection frequency is also enhanced since the RF signal being detected is close to
2f 0 . Numerical simulations predict that the sensitivity values in this case will also
be of the order of 10
5 mV/mW with comparably much higher detection frequencies
(4–6 GHz).
The values of sensitivity and detection frequency obtained by the above discussed
methods are summarized in Table 1. These results suggests that VCMA together with
parametric synchronization offer best combination of high RF sensitivity as well as
high detection frequency.
10 Spin Hall Nano-oscillators
In 1999, Hirsch revisited [164] a different phenomenon, the so-called spin Hall effect
(SHE), first described by D’yakonov and Perel’ in 1971 [165, 166]. The SHE can
produce a pure spin current in a direction perpendicular to a charge current [167,
168], which can, in turn, exert substantial STT on an adjacent magnetic layer. It
is thus possible to use the SHE in a nonmagnetic metal to achieve, in principle,
all the STT-related functions-such as magnetic switching [169, 170] and driven
magnetization precession [171, 172] that previously required a separate magnetic