Remote microwave monitoring of magnetization switching in CoFeB/Ta/CoFeB spin logic device

Abstract

Stable magnetic states of the MgO/CoFeB/Ta/CoFeB/MgO/Ta spin valve as well as transitions between the states were detected by microwave magnetoresistance (MMR) measured in the cavity of an electron spin resonance spectrometer. Advantages of this experimental technique are the possibility to study the orientation dependence of the MMR, the absence of the additional contact/sample interfaces, the wireless control of the spin valves, and the compatibility of the MMR measurements with ferromagnetic resonance experiments. The magnetic field dependence of the first derivation of the microwave absorption allows one to judge about the negative magnetoresistance of the layers and positive interlayer giant magnetoresistance. The obtained experimental results could be used for engineering of the microwave high sensitive sensors available for remote identification of the stable magnetic and logic states of the spin valves needful in medical spintronics to detect biological objects labeled with nanoparticles.

Effect of Fe/Fe3O4 Nanoparticles Stray Field on the Microwave Magnetoresistance of a CoFeB/Ta/CoFeB Synthetic Ferrimagnet

“…All of these experimentally determined energies were reported in our previous publications. , The d P ″/d H ( H ) dependence (Figure b) demonstrated four different areas separated by the same three critical fields in Figure a. The field dependence of d P ″/d H allowed one to detect changes in the magnetization of the layers by nonresonant microwave absorption …”

“…Step-like features of hysteretic behavior were reported previously in refs , . This effect is a direct manifestation of the interlayer coupling between the ferromagnetic layers, the switching fields of which coincide well with jumps on the d P ″/d H ( H ) plot.…”

“…Multiple d P ″/d H ( H ) dependences were recorded by varying the angle with a 5° step to avoid inaccuracy in sample positioning. Since ferromagnetic resonance (FMR) spectra were clearly determined in previous works, we used the resonant field of the FMR signal as an angular reference value to verify the angle . The sample was mounted in a node of the microwave magnetic field corresponding to a minimum of an electric microwave field.…”

“…Combining the highly sensitive microwave detection of magnetoresistance with the high effectiveness and sensitivity of GMR sensors to local magnetic fields allows us to develop wireless technology using microwave reflection/absorption to read the local resistivity of a sensor changed under the dipole fields of magnetically labeled objects. Changes in the quality factor (Q factor) of a microwave cavity containing a GMR platform covered with tested particles allow for developing a technique for the rapid and remote reading of a signal proportional to the locally demagnetized area of a ferromagnetic layer. , Theoretical estimations show that microwave detection can resolve the signal of a single nanoparticle of ∼100 nm size deposited on a GMR sensor …”

Influence of the magnetic field sweeping rate on magnetic transitions in synthetic ferrimagnets with perpendicular anisotropy

“…If the resistance of the sample is lower than the resistance of the microwave circuit (R C $ 190 X), absorbed microwave power P is proportional to sample resistance q and depends on magnetic field P $ q(H). [13][14][15] Thus, in our experiments, the derivation of absorbed microwave power measured by the modulation method was directly proportional to the derivation of specific resistance q of the sample dP/dH $ d(q(H))/dH. Magnetic hysteresis loops were recorded using an MPMS 5XL Quantum Design superconducting quantum interference device (SQUID) magnetometer.…”